Michael Murphy is the ultimate WASP in movies today. He has nurtured, refined, and exploited the role better than anyone else. He even played a character named Yale in Woody Allen's new hit, "Manhattan." For an Irish Catholic from California without a shred of the Eastern preppiness he exudes on the screen, you'd think he'd be ecstatic.

"I've got to stop it. Right now," he said recently over lunch in New York, his new home and spiritual base. "I've got to go out and play a blue-collar worker in a housing project in El Paso, something like that. I've turned down a lot of scripts since "Manhattan," which were more of the same thing - an urban guy in a tweed coat who leaves his wife and has an affair. I don't want to get typecast."

But it is tempting. He recently said no to $100,000 for a week of television work in Los Angeles for precisely that reason. If he lost any sleep over the decision, though, you'd never know it. "The money in television is fantastic, but so often the content is moronic," he said. "Besides, you do a few of those, and then you don't get asked to do the good stuff anymore. The good stuff means mediocre money by Hollywood standards and quality people. It means 'Nashville,' 'The Front,' 'An Unmarried Woman' and 'Manhattan.' These guys spoil you - Altman, Mazursky, Allen," he explained. "If I couldn't work with them, I suppose I'd work with new, young people; but I'm not in the least bit interested in the big, commercial movies."

Murphy claims he could be convincingly nasty on the screen, but one has to wonder. He looks like a man you'd want your daughter to marry, he looks naive. His smile, which he uses often and well, is as blinding as that of Doctor Kildare, with whom he appeared on numerous occasions during his television days in the mid-'60s. There is absolutely no menace in his face and very few lines for a man of 41.

But there is guile, and his screen roles exploit this. His characters lack passion. They are, by and large, shallow people who never express anger, like the figures in Jules Feiffer cartoons. Instead, they go south a lot when things get bad.

He made Jill Clayburgh throw up when he told her he was leaving her for a younger woman in "An Unmarried Woman." He epitomized political cynicism as the quintessential advance man in "Nashville." And professing great sorrow, he walked out on his wife and scuttled his best friend in "Manhattan."

This unattractive screen presence doesn't bother him. In fact, he says he relishes it. "It was great fun to play that scene in 'An Unmarried Woman' when I cry as I tell Jim I'm leaving her, he explained. My crying was so manipulative. The more obnoxious I was, the more I enjoyed it.

"But I don't like to see myself in that movie now. It was fun to make it, but not to watch it. The stockbroker character I palyed was a bad guy, a real heavy," he continued. "He's like a lot of men who wake up unhappy and don't know why, and they take it out on their wives. He was a whole separate story."

The only good WASP he has played was the young journalist sent from New York to do a story on the Centenarian, played by Cecily Tyson, in the title role of "The Autobiography of Miss Jean Pittman." And he wasn't wild over that one. "I was the only nice white guy in that," he said. "I wanted a twist at the end to make me look real, but it didn't work out. I suppose that if I played nicer people than I do, I'd probably be further along than I am today," he added, toying with his meal. "I don't think that people really like to watch these guys." But he can't resist them. For example, Murphy leans instinctively toward the Bruce Dern role of the returning marine husband of the Jane Fonda in "Coming Home."

"I was in the Marines, and I immediately gravitated towards this guy," he said. "The deck was stacked so heavily against him in that movie, and he really was a very complicated man."

If Michael Murphy is a new kind of light-heavy in movies, he broke into the screen with a bunch of more traditional roles in the blood and gore of "Combat," a television show in the '60s with which Robert Altman was connected. "Altman directed something like every third episode, I think," he said. "He played off of my face, the clean-cut image. I guess that's how it started."

Along with "Combat," Murphy did a lot of work on "Dr. Kildare," "Ben Casey" and many other of the TV paychecks of the '60s. He finally broke with television, except for rare appearances like the one in "The Autobiography of Miss Jean Pittman," after a bomb called "Nightwatch," in which he and Carroll O'Connor starred and Altman directed. It never made it, he said. Altman said he was through with TV, and I left with him.

The first of the 20-odd films that Murphy has made was an underwhelming experience called "Double Trouble," an Elvis Presley movie in which Murphy succumbed to a fatal karate chop from the king. He was very fast, he remembered. Murphy was reunited with Altman as the master of the Japanese whorehouse in "M*A*S*H," and became a part of the Altman menagerie in "Nashville" through the advance man role. He drew strong reviews for the job, in which he all but redefined the word "obsequious." He has been rising steadily, if slowly, ever since. To use his own words, Murphy keeps the nut small. He is unmarried, with no entangling alliances, no alimony or child support. He sublets an apartment in the East 70s from an actress friend and owns a small house in Malibu, which he hasn't lived in since he came East to do "The Front" with Woody Allen in 1975.

"I'd like to own an apartment here, be able to get away in August-that's all," he said. "I just don't see this Bel Air lifestyle with 14 Mercedes."

But, as he concedes, as goes the lifestyle goes the nut. "I'm living like a 22-year old now," he said. "If I were married with three kids, I'd hav to do a lot of things I don't want to do." He paused and then added, "But then if you base your whole life on movies, you're going to be a sad guy."

Murphy purported to be torn about this dilemma, but clearly not torn enough to go out and get married. He says he came close once, but he doesn't talk much about the women in his life. These days, he hangs around with Woody Allen, whom he desribes as a close friend, along with Allen's collaborator, Marshal Brickman, Jill Clayburgh and Paul Mazursky. Allen and he have virtually nothing in common, which Murphy says may be the secret of their friendship. Like the characters they play in "Manhattan," both seem to the struggling with their personal lives, if not their professional ones.

"None of us in 'Manhattan' are off the hook morally," he said."None of us were attractive. We all were brittle, intellectual jerks. The kid was the only one with dead-ahead morality."

"The kid" is the remarkable Mariel Hemingway, who caught Allen's eye in "Lipstick" and gave a stunning performance as his 17-year-old girlfriend in "Manhattan."

"But what was important about the movie was the ambivalence that you feel about the characters," he continued. "If they weren't very attractive, they were at least real."

If Murphy has anything in common with the other members of the Woody Allen troupe, it's Diane Keaton. Both grew up comfortably in California, and both have absorbed the residue of Allen's weightier intellect-like sponges, he says.

As the child of a tangential member of the Hollywood community, his decision to act was no great surprise to anyone in his family. "My father was very successful in selling surplus was stuff in Hollywood in the '40s," he said. "If you needed a pink swan for your pool, my father would have it. He used to supply John Ford with tents on location."

His family moved to Phoenix when he was in high school. Murphy graduated from the University of Arizona and then returned to Los Angeles to get his teaching certificate, after which he taught high school drama to support himself.

"Jeff Bridges was in one of my classes," he recalled, flashing one of his dazzling smiles. "I remember thinking later on, hell, this guy's up for an Oscar and I'm looking for a job."

By his own estimate, Murphy can live for the next couple of years without working, should the idea appeal to him and his nut remain small. He currently is doing his share to promote "Manhattan," and is directing an off-Broadway play called "Rat's Nest," which has been running since January.

Murphy's main goal in life right now, though, is to make his next move the right one. He's operating from strength at the moment, and he doesn't want to blow it. Having done a box-office clinker recently with Glenda Jackson and Oliver Reed called "The Class of Miss MacMichaels," he knows about pitfalls.

I talked myself into it because of her," he explained. "The director did 'Georgy Girl,' which I liked, and all of my scenes were with her . . ." His voice trails off because the movie was a bust, regardless of his rationalizations for making it. Murphy does have one plan in his head. It's about an aging baseball player who gets into trouble in Latin American while playing winter ball. Eastern-urban-preppy it is not. He'd like to produce it, to have more control over his life.

"I don't want to have to sit around anymore and wait," he said with as much conviction as he displayed throughout lunch. If he does have to sit it out, though, it won't be in California. He can't stand the place anymore. It is irnoic that this man who reeks of the "Forevery Young" aura of his home state, who says "real" rather than "really" before an adjective like a truce California, is now one of the more prominent purveyors of the "I Love New York" syndrome. He almost looks too healthy for this city. If he has adopted the Upper East Side of New York as his new home, he now must avoid it like the plague in his work. It is not easy.

"After 'An Unmarried Woman,' I said I was done with that kind of role. Then Woody came along with "Manhattan.'" CAPTION: Picture 1, no caption, by Donal F. Holway for the Washington Post; Picture 2, In "An Unmarried Woman" with Jill Clayburgh, "the more obnoxious I was, the more I enjoyed it."; Picture 3, Paul Mazursky and Murphy during the filming of "An Unmarried Woman."; Picture 4, Woody Allen and Michael Murphy in "Manhattan"