Charles H. Percy (R-Ill.), chairman of the Senate Foreign Relations Committee, convinced that nuclear arms control and a summit meeting between President Reagan and Soviet President Leonid I. Brezhnev are urgently required, is to begin hearings next Thursday that could be the most extensive and varied on the arms race in years.

His idea is to pull together the debate that is now sweeping the nation about how best to avoid nuclear war, then produce by May 18 a resolution to be sent to the Senate floor that could help focus the national concern and move the administration toward a course of action.

Not incidentally, it might also provide political shelter for Republicans who fear the administration's lack of progress on arms control so far could hurt them in this election year.

"Every point of view will be expressed," Percy said in an interview.

Secretary of Defense Caspar W. Weinberger is to lay out administration views on global strategy and the nuclear balance.

Former defense secretaries Harold Brown and James R. Schlesinger also are to testify, as are leaders of the Ground Zero movement, which seeks to alert the public to the perils of atomic war, and groups advocating nuclear freezes of various kinds. Secretary of State Alexander M. Haig Jr. and Eugene V. Rostow, head of the Arms Control and Disarmament Agency, also are expected to appear.

During these hearings, Percy said, he will press administration witnesses to put on the record "what they have said privately to me about their intentions to move ahead" with the U.S.-Soviet strategic arms reduction talks, or START. Percy said he feels those talks "will be under way by mid-year" and that the administration "will be willing to commit to that."

He said he expects an announcement of White House intentions on the talks to come "well in advance of" the president's scheduled trip to western Europe in June.

There have been no talks between the superpowers on limiting ocean-spanning, nuclear-tipped missiles and bombers since mid-1979, when President Carter and Brezhnev signed the SALT II agreement.

But that was never ratified in Congress and was essentially killed by the Soviet invasion of Afghanistan and then by the arrival of the Reagan administration, which viewed the treaty as "fatally flawed."

But in Percy's eyes, "This is the most important problem facing mankind and certainly the most important problem I'll ever deal with in the U.S. Senate. Time is running out," he says, "and it is paramount that we get this under way."

Time is short, for two reasons that Percy does not speak about publicly. One is that a sick and 75-year-old Brezhnev may not last much longer.

Another is that a year and a half of the Reagan administration have already gone by without strategic arms talks, so that a new round of these hard negotiations could well run over into still another administration with still another point of view, which leaves the Soviets skeptical.

During the interview, four events especially seemed to be shaping Percy's thinking.

One was his meeting with Brezhnev in Moscow in November, 1980. The senator said he came back from that meeting and reported to the president "that I saw a deep desire for arms control" in the Kremlin.

"Now you always have to assume it's on their terms," he said, but nevertheless "we should move as rapidly as we can when we have a president of the Soviet Union that is committed to arms control and wants it and really dramatically has a feeling for it. He talks in terms of what could happen to his grandchildren, his children in a nuclear age."

The second event took place 22 years ago when, as a young industrialist, Percy and then IBM chief executive Thomas Watson were touring the North American Air Defense Command headquarters and there was a false alarm indicating the country was coming under missile attack.

"There was panic," Percy said. "I saw it with my own eyes . . . . What do we do and how many minutes to decide? My God, the chance that you could have miscalculation."

There are two nuclear buttons, he says, one here and one in Moscow "and these two men Brezhnev and Reagan that have the power to make that decision have got to sit down across the table and talk and get to know each other." Thus there is pressure not just for arms talks but for a summit.

The third and fourth events are similar: the Soviet invasion of Afghanistan in 1979 and the imposition of martial law in Poland in December, 1981.

Both events derailed progress toward arms accords, one in the Carter, the other in the Reagan administration. Percy believes that it is unrealistic politically to submit a treaty to Congress for its approval when the atmosphere between the two nations is so poisoned by such events.

But he says he has talked at length with Haig and others and will push hard at the hearings for an end to what is commonly called "linkage" because the negotiations, at least, are too important to be sidetracked by international flare-ups.

"I have urged that we not wait for the Soviets to be acting every place in the world in accordance with our code of conduct and ethics. Nuclear warfare and the horror of it and the possibility of miscalculation is so great that it transcends all other problems. Starting talks should not be a reward for good behavior," he says. "We have . . . an arms control agency set up by law for that purpose," he adds, "and it shouldn't be subject to every election and every event that occurs in the world."

Some Senate staff specialists express the view privately that the Reagan White House has, in fact, wasted a year and a half in even getting talks started.

By mishandling new weapons programs, it would also go into new negotiations with a weak hand and few bargaining chips because the MX missile is in trouble and old Titan missiles and B52 bombers are being taken out of operation unilaterally.

On balance, Percy says, "I would have liked movement to have gone faster." But he says he is convinced that the president "genuinely wants real reductions . . . wants to sit down face to face with Brezhnev . . . and that his policy is going to prevail now" over the lower-level squabbling that has gone on.

Reagan, Percy says, does have respect for differing points of view and each administration needs time to work things out. "There's skepticism among some members of the administration that the Soviets will ever agree to what they the U.S. officials think has got to be the basis of an arms control agreement. Some of them are so extreme that they are the kind of people that would never make a deal on anything except their own terms."

But Percy says that both the United States and the Soviets are continuing tacitly to observe the terms of the unratified SALT II treaty, under which the Soviets would have been required to dismantle some 250 of their missiles by now.

As for the Soviets, he says, "the economic situation has worsened dramatically" since 1979. "I really think they need to find a way to put a cap on this unlimited expense" of the arms race "and the strain that Poland has put upon them, So I think there is a mutuality of interest here and that's the only way you can ever have a deal."