The United States should make a small gesture of good will to Poland now, in the immediate aftermath of Pope John Paul II's dramatic visit, rather than wait, as President Reagan prefers, to see if Polish authorities ease internal repressions.

That is the view of specialists outside the Reagan administration such as Zbigniew Brzezinski, President Carter's Polish-born national security adviser, and Richard von Weizsaecker, the mayor of West Berlin and a foreign policy expert within West Germany's ruling Christian Democratic Union party. Von Weizsaecker is visiting Washington now.

Both specialists, in recent interviews, suggested that lifting the U.S. sanction against Polish fishing in American waters, for example, would be the kind of small step that would signal good will. Yet the West would still keep in place, for future leverage, the more significant economic sanctions imposed after Poland imposed martial law in December, 1981, and outlawed the free Solidarity trade union.

The idea behind a quick U.S. step, the specialists say, is to encourage Polish leaders to move toward moderation and to allow those who argued for the controversial papal visit to show their bosses in Moscow the benefits of a more moderate line.

"I would certainly be in favor of starting with a very small, unilateral signal," said von Weizsaecker, "which is viewed by the Polish people as to their benefit yet which is not meant to be unfriendly to the Polish government."

"You do not want to go ahead with one unilateral gift after another," he said, but "I think a small but meaningful gesture would be understood by the Polish population and it would not in any way commit the American government on the side of the Polish government, in case that government went in the opposite direction."

Administration officials and outside experts agree that the pope's visit to his homeland last week presents a potentially important new foreign policy opportunity for this country and its allies in relations with Poland. But they differ in important ways on tactics and timing.

In a speech Thursday in Chicago, Reagan said that "if the Polish government takes meaningful, liberalizing measures, we are prepared to take equally significant and concrete steps of our own." The Polish government yesterday protested Reagan's remarks in Chicago, Reuter reported from Warsaw. The official Polish news agency PAP said that the speech represented interference in Poland's internal affairs.

Ever since the crisis in Poland, this country and its allies have demanded not just a suspension but a lifting of martial law, release of political prisoners and renewed dialogue between the government and the labor movement and the Catholic church.

Administration officials say that they are "heartened" by the way the papal visit went, but that they will maintain a basic wait-and-see attitude with respect to the future actions of the regime of Gen. Wojciech Jaruzelski.

But Brzezinski says he believes tactics should be developed for a potentially crucial period already at hand, and he and Weizacker both argue for faster action.

"The papal visit has created the potential for a new situation in Poland and much depends on how we exploit it," Brzezinski said. "Jaruzelski will be under pressure from hardliners" inside his own government "and from the Soviets to reaffirm strict ideological conformity and maybe crack down even further."

The pope delivered several hard-hitting speeches in his homeland stressing freedom and human rights and Jaruzelski, who approved the visit, has his neck way out, both government and outside experts here agree.

"Jaruzelski can only demonstrate the usefulness of the visit if it can be shown that it has led to some reduction of external pressure on Poland," Brzezinski said. "That argument can even have some impact on Moscow because the Soviets are not happy about having to carry the Polish economic burden."

"If we don't react and we insist upon maximum and instant concessions," Brzezinski said, "we play into the hands of the Soviets who will make the case that the papal visit simply strengthened the forces of reaction" inside Poland.

The former Carter adviser favors a three-stage policy.

First, he said, "lift some sanctions immediately so Jaruzelski and company can claim some credit."

A second stage would extend to July 22, which is national day in Poland. There are rumors of some political amnesty for prisoners on that day and a possible lifting of martial law, which was suspended but not totally abolished last December.

"If between now and July 22, there is no crackdown and no further movement to some political trials that have been scheduled," Brzezinski said he would advocate a second step in which this administration "indicates willingness to consider reviewing the debt schedule" associated with Poland's massive $28 billion debt to western nations.

Finally, he said, "if there is movement toward serious negotiations" between the government and labor aimed at restoring the liberal trade union charter agreed to in 1980, "then we should undertake, along with western Europe, a larger economic aid package designed to stabilize the catastrophic economic situation" in Poland.

Administration officials, however, remain skeptical. "There are still lots of people in jail," one said, "there is still no dialogue with their own people and martial law has still not been lifted." A lot of what Jaruzelski has done so far in the name of liberalization is "cosmetic," he said.

"So we are waiting. We talk in the conditional tense. The 'if' is still there in what the president says. I don't know who is going to step first, but it seems pretty safe to assume there has got to be more movement on the Polish side. And we won't take action without our allies, so it could be a slow process."