It isn't exactly a photograph of the pin-up poster variety like the one with former Baltimore pitcher Jim Palmer in his sexy briefs, but William (The Refrigerator) Perry has his own underwear ad. And in this one the Chicago Bear poses, appropriately, with a real bear. Perry is promoting long underwear, and given the brutality of Chicago's winters, it's understandable.

It seems that the Bears' equipment manager, desperate for a set of long underwear that would fit the substantial defensive tackle, called the Royal Textile Mills for help. Someone there looked up and said, "That would make a great ad: 'We Keep the Refrigerator Warm.' " So Perry and a 100-pound trained bear (which next to Perry resembles a lap dog) posed for the ad, which will appear in trade publications and in sporting goods stores. Who knows how well a poster might sell? Palmer had better not rest on his laurels. Wicker's Biography of Nixon

New York Times columnist Tom Wicker has just signed with Random House to write a major biography of Richard M. Nixon that will focus mainly on the former president's foreign-policy achievements and what led up to them. Wicker, who was The Times' Washington bureau chief from 1964 to 1968, just before Nixon became president, pointed out that Nixon's political career spanned four significant decades in the nation's history.

During that period, Wicker said, Nixon was involved in more important foreign-policy development at a higher level than any other American. His first administration saw the opening of relations with China, SALT I talks and the beginning of de'tente. The publishers expect the as-yet-untitled Wicker book to be published in 1987. Wicker is the author of 11 books, his most recent a Civil War period novel, "Unto This Hour," published in 1984. Two of his better known books have been a novel, "Facing the Lions," and a book on the Attica prison revolt, "A Time to Die." Autobiographies That Sell, Sell, Sell

Autobiography is clearly the place to go in the book world. On Friday, the Bantam Book "Iacocca: An Autobiography," by Chrysler Chairman Lee Iacocca and William Novak, goes into its 48th printing. That means 2.5 million hard copies of the book are in print since it came out 14 months ago. This has been a good year for Bantam. Another of its best sellers with an equally unexciting title, "Yeager: An Autobiography," goes into its 16th printing Saturday. Both books were produced by a similar formula that obviously works. In the six months since the book by Gen. Chuck Yeager, the first man to break the sound barrier, and Leo Janos was published, a million copies have been put in print.

Both books are doing so well that Bantam has no immediate plans to come out with paperback editions. Bantam spokesman Stuart Applebaum said that only three times in this century has there been a book as successful as the Iacocca book. The all-time champ is "Gone With the Wind," published in 1936, with 6 million sold, followed by the 1970 novel "Jonathan Livingston Seagull" with 3.1 million copies and Norman Vincent Peale's 1952 "The Power of Positive Thinking" with 2.6 million. End Notes

Look for various presidential preference polls in this town right up to 1988. This past weekend a new group of Democratic Hill staffers called the New Democratic Forum had a party and raised two questions: Who do you think the Democratic nominee will be? Who would you like the Democratic nominee to be? On "who do you think," Sen. Gary Hart received 41 votes, New York Gov. Mario Cuomo 20 and Sen. Edward Kennedy 17, followed by Sens. Joseph Biden and Bill Bradley and Virginia Gov. Chuck Robb. On "who do you want," Hart led again with 26, Cuomo had 22 and Kennedy and Biden had 10 each, followed by Robb, Sen. Dale Bumpers and Rep. Richard A. Gephardt. Who said the Democrats would have some new ideas for 1988? . . .

President Reagan and his wife Nancy last night attended a performance of "Aren't We All?" starring their old friends Rex Harrison and Claudette Colbert. Harrison dined with the Reagans Monday at the home of former CIA director Richard Helms, and Colbert is to have Christmas dinner at the White House . . .

It would be too much to expect the arrogant Claus von Bu low to send a traditional Christmas card. His cards have a photograph of him and his daughter Cosima on the front. They are seen leaving a Providence, R.I., courthouse on June 6, the day his second trial went to the jury that eventually acquitted him of twice trying to kill his heiress wife Martha (Sunny) von Bu low, who is in an irreversible coma in a New York City hospital. Von Bu low has a big smile on his face and inside is the traditional "Merry Christmas with many good wishes for the coming year" . . .