`IN LOVE' AND BULLOCK : GIRL-NEXT-DOOR ACTRESS REINS IN HER USUAL EXUBERANCE FOR WARTIME ROMANCE.

Byline: Bob Strauss Daily News Film Writer

All hemmed-in, both physically and emotionally. This is not the Sandra Bullock America knows and loves.

Whether sexy (``A Time to Kill'') or sprightly (``Speed,'' ``While You Were Sleeping,'' ``Demolition Man'' and just about everything else), Bullock has become Hollywood's top young actress on the strength of no-sweat charisma and girl-next-door accessibility. Full of fun and energy, she turns most movies she makes into parties, both on and off the screen.

So watching Bullock reining in her bright, contemporary exuberance for the historical romance ``In Love and War'' is pretty disorienting. She thinks so, too.

``Mentally, it was absolutely the biggest challenge yet,'' Bullock says of playing Agnes von Kurowsky, the Red Cross nurse whose affair with ambulance driver Ernest Hemingway in World War I Italy inspired the novel ``A Farewell to Arms.'' ``It was a definite transformation of everything that I knew as comfortable. But with someone like Richard to guide you, the abandonment was a lot easier. When a lot of directors say `trust me,' they totally let you fall on your face; but in this case, you could see the work that he's pulled out of others.''

Richard is Richard Attenborough, the Oscar-winning director of ``Gandhi'' and such other historical films as ``Shadowlands,'' ``Chaplin,'' ``Cry Freedom,'' ``A Bridge Too Far'' and ``Young Winston.''

``In Love and War,'' which is based on Henry S. Villard and James Nagel's book of the same name, recounts Villard and Hemingway's encounter with von Kurowsky when both were hospitalized near the end of the Great War. Chris O'Donnell plays the young literary genius in the movie; Mackenzie Astin is his friendly rival and eventual chronicler.

According to Villard, who died this year just as his son, Dimitri, was producing the film, all of the wounded young men fell in love with von Kurowsky. She denied for decades afterward that her relationship with Hemingway was anything more than friendly, but letters and diaries she willed to Villard indicate otherwise.

And even though their romance hardly ran the same consuming, tragic course as Frederic and Catherine's in ``Farewell,'' it seems evident that the budding author's frustrated affair with the older nurse (she was 26, he was still a teen-ager) had a damaging effect on all of his subsequent relationships with women.

We can buy Bullock as the belle of the wounded ward, no problem. As for the rest of the stuff, well, that's where the work comes in.

``I think everybody knows that I'm very physical, always rely on comedy, always rely on the comforts of anything contemporary,'' Bullock admits. ``It's easy when it's in your everyday behavior. But when you're going back to a time that you just weren't a part of, you have to internalize so many different things.

``There was a different body language back then,'' she says. ``A way that you carried yourself, a way that you spoke, a way that you allowed yourself to react to men, women, your job place. We had to start from scratch. We had to sort of redefine me, in the sense that everything that was big and animated had to be lost.''

To keep her in character, Attenborough went so far as to draw big Bs in the air with a finger whenever he felt Bullock's standard mannerisms were creeping into the performance. And then there was the hilarious - but instructive! - spectacle of the elfin, 73-year-old Englishman kissing his own forearm, to demonstrate to his young stars how a passionate love scene might have played in 1918.

``It was appreciated, actually,'' Bullock recalls. ``When you see two people's faces smash into each other, that represents a whole different time. Visually, it was important that we established something like that. It can't be groping because of the times. We wanted this to be an opening up, sort of an unwrapping of a gift.''

A gift that, by the time it reached the invisible-thong-bikini stage, included a typical Bullock touch - a Post-It note, unseen by all except leading man O'Donnell, that read ``Danger: Keep Out.''

That's more like the brash sport we know and love. But Bullock claims there was minimal goofing around on ``In Love and War's'' gorgeous location in the Italian Alps. In fact, the whole experience brought out a more reflective, sophisticated aspect of the actress' character. Although she's made her fortune as Hollywood's favorite all-American gal, Bullock is actually the product of a cosmopolitan upbringing, having spent many years in her opera-singer mother's native Germany as a child.

``I feel very comfortable in most European countries,'' she says. ``I don't feel like a native, but then again I don't feel like a native in the United States sometimes, either. But it was great that we started the movie off where we did. The streets, the atmosphere; you get this sense of timelessness that you can't find anywhere else.''

Must have been nice, especially considering what Bullock was in for next: ``Speed II,'' which is currently shooting off the Caribbean island of St. Martin.

That one, which is set on a ship, has nothing to do with holding oneself properly or exquisitely delicate kissing.

``I have more cuts and bruises and scrapes,'' Bullock laments. ``More blood has been lost ... ''

And some bad blood aroused, it's reckoned, when Keanu Reeves declined to return for the sequel along with Bullock and director Jan De Bont. Moody thespian Jason Patric, most recently seen in ``Sleepers,'' is Bullock's new co-star.

``He made the absolutely right decision for himself,'' she says of Reeves' refusal to participate in the blockbuster sequel. ``I totally agree with his decision. But I committed to Jan. Jan gave me a great career, and I wanted to do this. I needed it.''

Bullock won't go into more detail about why she backs Reeves' decision or why she feels she needs to make another big action spectacular. After all, she doesn't seem too concerned about maintaining her box-office dominance, and she just comes off so practical and well-adjusted that greed wouldn't seem a deciding factor, either.

For example, Bullock dismisses suggestions that she's replaced Julia Roberts at the top of everyone's A list (``God, I hope not,'' was the blushingly delivered exact quote). And she's perfectly contented to acknowledge that superstardom is cyclical at best and impermanent by nature.

What Bullock makes a stronger case for needing right now is a life as fulfilling as the acting career has been.

``I've done films that I could relate to, which also seemed to be things that others could relate to as well,'' she notes. ``I think I've done a nice gamut and range of different styles in a short period of time. I love that, and I love to work. But now, it's more a matter of sit back and be involved in storytelling that's more specific and more artistically challenging.

``I've found that I am the most alive, actually, behind the camera,'' reveals the actress, who's founded a production company, Fortis Films, and recently directed her first short subject, ``Making Sandwiches.'' ``But I've really depleted a lot of what I know; I haven't evolved and enjoyed my emotional life some more to add to another huge string of acting projects.

``I really need to pull back and just live a little bit,'' she admits. ``Grow up some more and whatever.''

But will America really go for a more mature Sandra Bullock? Growing as an actress could, after all, mean the loss of that special something that makes her such a great movie star.

``You know what?'' she says with a shrug. ``I don't know what it is people like about me, and I'm so scared to think about it. There was something Hemingway wrote about (F. Scott) Fitzgerald, I believe. He compared him to a butterfly, that he didn't know what his gift was. But once he figured out what the gift was, it almost broke his wings to become aware of his beauty, and he couldn't fly anymore.

``So I don't know what it is. And I'm not gonna ponder on that one.''

CAPTION(S):

3 Photos

Photo: (1--Cover--Color) Simply Sandra?

For `In Love and War,' Bullock gets serious as the nurse who turns Ernest Hemingway's head

(2) ``Mentally, it was absolutely the biggest challenge yet,'' Sandra Bullock says of playing Red Cross nurse Agnes von Kurowsky in ``In Love and War.''

(3) The affair between Agnes von Kurowsky (Sandra Bullock) and ambulance driver Ernest Hemingway (Chris O'Donnell) in World War I Italy inspired the novel ``A Farewell to Arms'' and ``In Love and War.''