President Reagan, who was insulated by his staff from spontaneous exchanges with reporters during much of the 1982 congressional election campaign, has told White House officials he wants to give more news conferences and interviews.

Yesterday, the president kicked off the new approach with a 14-minute question-and-answer session in the Oval Office about the MX missile, the economy and other subjects. White House deputy press secretary Larry Speakes said it marked the beginning of more frequent contact between Reagan and reporters.

But Speakes cautioned that this would be short-lived if the impromptu news conference in the Oval Office became raucous. He instructed reporters not to compete with each other in shouting questions as Reagan sat at his desk.

Speakes also set a strict 10-minute time limit. But Reagan, who often likes to take questions even when his staff is trying to cut them off, allowed the session to continue for several more minutes.

Asked whether he would hold a formal news conference next week, Reagan said, "That, or I think more things of this kind in between, so that you don't have so much time to think of ammunition."

Some of Reagan's close associates say they believe he has demonstrated in his political campaigns an ability to handle frequent news conferences. When he was governor of California, Reagan held them weekly.

Although he stumbled in his first year as governor -- once not being able to identify the status of legislation his administration had proposed -- the news conferences also were credited with shaping Reagan's decisions.

During the 1980 presidential campaign, after a series of embarrassments just before Labor Day, Reagan's campaign managers clamped a lid on his access to the media. He went from four or five news conferences a day to quick curbside exchanges with waiting reporters.

The purpose of putting Reagan under wraps then was to help restore his shaken confidence and to get his message out unaltered. A few weeks later, when the strategy seemed to have worked, he returned to a more relaxed give-and-take with reporters.

There was a similar tightening-up this autumn, after Reagan made some slips at news conferences, when White House officials again wanted to get his "stay-the-course" message across without the interference of reporters' questions.

Even some of the president's ceremonial activities at the White House were closed to cameras and reporters.

Both Speakes and communications director David R. Gergen argued after the midterm congressional campaign that Reagan should again meet with reporters more frequently. Reagan has held far fewer formal news conferences than have other modern-day presidents.

One result has been that reporters often shout questions at Reagan in so-called "photo opportunities," even when visiting dignitaries are in the Oval Office. White House officials hope that by holding more sessions such as the one yesterday the photo sessions will not be interrupted as frequently.

Yesterday, Reagan had on his desk a memo pad printed, "No More Mr. Nice Guy." It was a gift, he said. "Some people just think that I've got to stop being so nice to all of you."