Paul Winfield - the actor who won an Academy Award nomination for his role in "Sounder" and recently showed up on television as a Vietnam vet looking for his lost son - doesn't know who he is.

Maybe it's because he's illegitimate ("I'm a love child. That sounds so much better than ellegitimate.") Maybe it's because he's been going to psychiatrists off and on "since I was 3." Or maybe he's a black Diogenes looking for the truth - an honest man, an honest woman. Especially that honest woman.

"I'm not literally looking into who I am. Under the circumstances, tracing my background would be an embarrassment to the family," Winfield said yesterday with a grin. "But I'm still trying to find out who I am as a person."

At 35, Winfield, who has neither the street cool of a Richard "Shaft" Roundtree nor the dashing romanticism of a Billy Dee Williams, is a single man. What he, does have is a vast and winning grin that gives his characters instant audience sympathy. But his status as a single bothers him. Though he has been dating Cicely Tyson, his co-star in "Sounder" ("We both see other people"), he has trouble, maintaining long-term intimate relations because of what he calls his need for "uncritical affection."

"I tend to stifle as opposed to cultivate. And I'm very jealous," he said. "Probably because I'm neurotic. But acting has been the great escape. You can always take a peek at the end of the script to see how it all comes out. We don't have that luxury in real life."

Winfield, whose slightly protruding puppy-brown eyes look sad when he says this, tries hard to keep in touch with real life. He keeps his digital watch set on California time because "It's my link with reality" and most of his friends are not actors. "A lot of them are carpenters and plumbers right now because I'm renovating my house in San Francisco. I hired one man and I supply the labor," he smiled.

"A lot of my friends spend a lot of time trying to stay out of jail, for all kinds of reasons. One of my closest friends is a woman named Alma . . ." He rifles through his black address book to look up the last name. "Brechtsnider, who works in a drug rehab center in Haight-Ashbury. I have a terrible time remembering names.

"I was engaged to be married when I was 23 and we had one of those announcement parties. I turned to introduce my fiancee and the name just wouldn't come. Needless to say, the relationship didn't last."

Winfield said that for ten years he used the excuse that he was "too busy" for a serious relationship, but now "That's a bunch of bull -. When you look at the whole history of the world, my acting is not that important."

But for the past 15 years, acting and the movies and theater, particularly theater, have been that important to Winfield. At one time, he thought that being on stage was the crucial thing in his life. Now he doesn't know.

"Realistically, I could be in a Broadway play with standing room only, but more people see you in a half-hour television show. At the moment I'm very fortunate in the amount of work I've had which doesn't leave time for tripping the light fantastic on stage."

Winfield, though, is particular about the kinds of roles he plays. It's part of his search for self and one of the reasons he doesn't do blaxploitation films. Nor does he like the way such films portray women. Once again the search for the woman becomes important.

"I chose not to be in those roles because they were cardboard stories. There were no relations with women that weren't exploitative. There was no room for tears, so from an acting point of view I didn't know how to approach them.

"But I did one, 'Trouble Man'. No, it wasn't exploitative," he said. " . . . Oh, yes it was. But I did it as a personal favor to Ivan Dixon, who was the director. It was an entirely black production and it gave the opportunity for a lot of blacks to get accreditation."

Winfield, who would like to direct and produce eventually, laments the lack of blacks in those positions.

"It comes down to the distribution of films. There are really fine films - both black and white - which you'll never see. Film companies are controlled by a very small group of people, their sons and relatives, who have achieved a certain amount of power. They tend to remake the same thing over and over again."

Even though "Sounder" was touted as a true-to-life black movie, Winfield said that because the producer and the director and the writer of the book weren't black, the movie was not what it could have been. He said that one of the reasons he has taken his current role in "Twilight's Last Gleaming" is "to learn how to put together the money and the people."

"Twilight", in which he, Burt Lancaster and Burt Young, as ex-convicts, invade a SAC missile base and hold the President of the United States and a Titan ICBM hostage, has its premiere, here Feb. 6.

"I've found a few properties that I would like to produce, but I think you need the pimp mentality," Winfield said about his potential career as a producer. "You need the ability to sell your own mother to produce. I haven't reached that point yet." He pauses. It's that grin again. "But I'm working on it."

Winfield is also still working on who he is. Raised in Watts, his search began because "My mother read a lot of books and she wasn't sure she was raising me right. I was pretty precocious, so she sent me to a psychiatrist." His mother eventually married and Winfield has two half-brothers and a sister; perhaps the competition for his mother's attention explains his need for "uncritical attention", he says.

Now he goes to transactional analysis whenever he's in San Francisco for what he calls "mental facelifts." Mostly he goes because "being alone keeps me awake at night.I wonder why the last affair didn't work out. What I did wrong. What she did wrong."

And then there's always acting to help him find himself. He said the character that comes closest to what he wants to be is the man in "A Hero Ain't Nothing But a Sandwich," which he made with Cicely Tyson.

"It's about a contemporary black family, a man who is living with a woman who has a son. The son and the character I play are both competing for the attention of the woman."

Even though he identifies with the situation, Winfield's own life is currently nothing like that. His closest friend is his dog "Bucky" (for Buckingham), a cocker spaniel that he bought when he played Buckingham in Richard II on Broadway.

"I bought him because it was the first time I'd been on Broadway and the play got awful reviews. I got good ones, but I wanted everything to be perfect. I was feeling depressed and whenever that happens I like to go look in pet shops. So I bought him."

Still the search goes on for that special friend, that one woman who provides "uncritical affection."

"I guess I would marry her if I had such a friend."