EARLY IN THE Reagan administration, two aides who had helped prepare the president for a news conference were watching on television when a reporter raised a potentially difficult question. Reagan repeated it, stalling for time, and then launched into an answer that in no way resembled the information in his briefing book.

"Hold on to your seat belt," said one aide to the other. "The governor's winging it again."

Increasingly, Reagan's habit of "winging" answers to news conference questions has become a disturbing one within the inner circle of the administration. While some within this circle dismiss critical comments about Reagan's responses as a "press issue," others are frankly worried about whispered concern that Reagan is misinformed on major policy questions or that his grasp of issues is slipping.

Reagan added some fuel to the fire last week when he mangled some unemployment statistics and misremembered a key provision of a controversial abortion bill he had signed as governor.

But almost every Reagan press conference -- and he held only seven in l981, compared with 22 by President Carter during his first year in office -- has produced some strange statements.

On June 16, 1981, at his first press conference in three months, Reagan described Syrian surface-to-air missiles in Lebanon, which are used for defensive purposes, as "offensive weapons."

At the same press conference Reagan was uncomfortably vague about the question of whether a nuclear war could be limited to Europe or would inevitably spread to a confrontation between the superpowers. When Reagan was asked this question at an interview with out-of-town editors on Oct. 16, he replied: "I don't honestly know. I think, again, until someplace -- all over the world this is being, research going on, to try and find the defensive weapon. There never has been a weapon that someone hasn't come up with a defense."

On Dec. 17, when Reagan was asked whether he agreed with his Justice Department's attempt to overturn the Webber ruling -- a Supreme Court decision allowing voluntary affirmative action agreements between management and unions -- Reagan confessed that he had never heard of the noted case. After a reporter summarized it for him, Reagan said: "This is something that simply allows the training and the bringing up so that more opportunities are there for them in voluntary agreement between the union and management -- I can't see any fault with that. I am for that."

It turned out, however, that his administration was not. More than two weeks later, on Jan. 3, White House aides said that Reagan agreed with the Justice Department in its position that the decision should be overturned.

Reagan's answer on Webber is a good example of "winging it." Even though the president should have been forewarned by the reporter's statement that the Justice Department was trying to overturn the decision, he said what came into his head, oblivious to the policy implications of his own answer.

The president's problems at press conferences and also in some interviews stem from a unique blend of misinformation, candor and a photographic mind that sometimes betrays its owner.

"He has a mind that locks in on facts and figures," says a White House aide frequently involved in the briefing process. "He pulls them from the card catalogue in his mind and nobody knows where they came from."

Reagan also has a tendency to over-answer questions, a habit which his California communications director Lyn Nofziger vainly tried to break. Because Reagan genuinely desires to please his audience, even when it is composed of uneasily pleased reporters, he answers questions that more prudent politicians would dodge.

Once Reagan gives an answer it becomes forever embedded in his mental card catalogue, waiting to be retrieved by some appropriate stimulus. Sometimes the long-stored answer comes forth in a more dramatic guise, to the dismay of those who hear it.

Reagan's asssociation of the New Deal with fascism is one example of this process. During the 1930s, Republican critics of Franklin Roosevelt frequently pinned the "fascist" label on some of the more centralizing aspects of the New Deal. Reagan used to say that there were tendencies within the New Deal resembling fascism, a controversial but historically respectable view.

However, when Reagan dredged up this answer Dec. 22 during an interview on public television with Ben Wattenberg, the contention had been elevated to an accusation that prominent New Dealers "espoused" fascism, which is historically groundless.

Such statements may express the preference of Reagan's mind for a dramatic statement rather than a dull one. It is the flip side of being The Great Communicator. In his years as a speaker on what he used to call "the rubber chicken circuit," Reagan developed a knack for dramatic illustration and an endless flow of statistics which earned him the sobriquet of "the Reader's Digest of politics."

"History shows that when the taxes of a nation approach about 20 percent of the people's income, there begins to be a lack of respect for government," Reagan would say on the campaign trail. "When it reaches 25 percent there comes an increase in lawlessness."

History does not in fact show this. Many European countries have higher rates of taxation than the United States and less crime.

Reagan always acted a little surprised when reporters took such statements literally. He still does. When a spate of stories appeared during the 1980 campaign questioning Reagan's use of facts and figures, he described the process as "journalistic incest."

Last week, White House assistant for communications David R. Gergen said that stories about Reagan's misuse of statistics "tend to be inside baseball" with the press and asserted that they have had no visible impact on Reagan's political standing.

He has a point. Throughout his public career, Reagan's use of statistics and his general level of information has been persistently suspect but rarely damaging.

In the 1980 campaign Reagan said incorrectly that Vietnam veterans did not receive college benefits. He quoted from a nonexistent General Accounting Office report about government waste and fraud. He misstated the cost of government health service for the needy. He criticized the United Nations Commission to Iran for having a Libyan member, which it didn't. He discovered more oil in Alaska than there is in Saudi Arabia. He said that the tax cut proposed by President Kennedy in 1963 and enacted the year after his death was the same as his then-proposed 30 percent reduction, when in fact it was 18 percent.

On and on reeled the statistics, without effect. All of these statements were reported, some several times. None of them had any visible impact on the Reagan candidacy. His winning personality tended to make objections to the quality of his information seem like nitpicks from the press. One political aide even described Reagan's misstatements as "part of his charm."

Now, however, there is concern that further verbal fumbling by Reagan may contribute to the impression of a president whose grasp is slipping. The White House staff has moved to upgrade Reagan's understanding with Monday issues luncheons. The president is given the briefing books for these luncheons to study over the weekends. On weeks when a press conference is scheduled, Reagan receives still another briefing book and a rehearsal of probable questions before his meeting with the press, which appeals to Reagan's preference for verbal give-and-take.

The new system is an experiment that some aides hope will restore Reagan's fading Sacramento reputation as a master of the press conference.

But there are significant differences between the procedures of both the press and Reagan in Sacramento and in Washington. During his eight years as governor of California, Reagan usually followed a pattern of weekly press conferences, which made it easier for this staff to anticipate the questions. There were few questions about foreign policy. And the California press corps followed a long custom of exhausting one subject before it moved on to another instead of the scattershot system used at Washington press conferences.

No matter what the process, Reagan has never liked to cuddle up with his briefing books for very long. He will be 71 next month. In a way he is a prisoner of his own achievements. He has always succeeded in winging it, and he is not likely to change now.