Any American interested in foreign policy who visits Moscow these days will receive plenty of free advice from Soviet friends about how the Reagan administration should behave, but what impressed me during a recent trip to the Soviet Union was a request for some help in trying to figure out what a second Reagan term, if it materializes, would bring in the field of Soviet-American relations. No doubt Andrei Gromyko had a similar curiosity when he spoke with the President and Secretary of State George Shultz. The Soviets fear that ''the train has left the station,'' a Moscow expression meant to convey a sense of lost opportunities in the first Reagan administration and the possibility they cannot be retrieved in a second. How might one respond to such pessimism? The train has not quite pulled out, but some late-arriving passengers are talking themselves into this point of view.
First, one has to remind Soviet colleagues that there has been an overreaction in Moscow to Reagan's ideological rhetoric, after thinking quite the opposite about the first Reagan administration. While it is hard now to find any Soviet who will confess to it, there was initially a feeling in Moscow that Reagan would turn out like his allegedly ''realistic'' Republican predecessors, Presidents Nixon and Ford, a business-as-usual person. Disappointment in this undue optimism has probably been partly responsible for the pessimism one finds these days in Moscow about the future course of Soviet-US relations. There seems no more disillusioned person than a realist. The so-called realities of Soviet-US relations always have something to do with ideas and not simply with crude pragmatism.
Second, a number of signs point to a slowdown in the Reagan ''mandate'' of 1981 as the administration prepares - perhaps prematurely - for its second term in 1985. One has to remind Soviet colleagues that it is probable a second Reagan administration will be more pragmatic after its first four years of enthusiasm. Yet it is extremely unfortunate that Soviet analysts may have reversed this trend, arguing for pragmatism early in Reagan's tenure and now seeing nothing but ideology. They make a point of the 1984 GOP convention. Perhaps the meetings with Gromyko in New York and Washington the week of Sept. 24 have helped correct this deficiency in Soviet analysis, but one cannot be certain. A Reagan interest in accommodation with the Soviet Union may well be a function of a mandate that has lost its fast pace and now appears headed for still more controversial times in a likely second term.
Third, one wants to tell Soviet friends that the train has not quite left the station and that their argument to the contrary only leads to self-fulfilling consequences. There is always more than a little bit of helplessness in Soviet thinking when it comes to such self-fulfilling prophecies, particularly when ideology becomes paramount as it now is; but one worries that a great cosmopolitan city like Moscow, so given to urbane political conversation, may be talking itself out of opportunities to do business with a second Reagan administration. Now is a propitious time in US politics to set a positive agenda for Soviet-US relations in the last days of the first Reagan term, but one gathers in Moscow that the burden of proof is on those who wish to be positive rather than negative. The ''I told you so'' crowd, whose ranks are swollen by a number of converts from an earlier optimism, are having an easy time in high Soviet circles.
Fourth, the chief evidence that the Reagan mandate has slowed comes in the very field where Soviets find the most fault with the President, the areas of ''military superiority.'' Even while the crescendo of Soviet criticism grows over tentative Reagan ventures into the world of ''star wars,'' the debate in the US over the new fiscal year 1986 Defense Budget promises to be an exciting one where one of the main questions will be the Reagan performance on arms control. The current administration may slip by in the 1984 election without too much trouble on this issue - although this issue will be more damaging to Reagan than most others - only to find itself in the midst of a congressional imbroglio on the same topic.
Reagan's own military advisers are divided on the virtues of space defense and these very divisions may be contributing to administration second thoughts about various aspects of the program. One wants to tell interested Soviets that early in a new Reagan administration, if this comes to pass, there will be an excellent opportunity to negotiate with the President on space weapons, if only Moscow can talk itself out of its fixation on the earlier Reagan peace-through-strength mandate. Unfortunately, certain Reagan administration officials continue to espouse the latter simplistic doctrine.
Recent conversations in Moscow seem to point toward a Soviet policy that may have talked itself into a view that the train has left the station and many passengers are now stranded with no hope of opportunities to improve Soviet-American relations in the foreseeable future. One hopes this view is only a dramatic way of making the point that there is little time left for constructing a positive agenda for Soviet-American relations in a new Reagan administration, if Reagan should win in November. One worries, however, that in the Soviet Politburo, party Central Committee, foreign and defense bureaucracies , research institutes, media circles, and among ordinary citizens, some very articulate pessimists have taken charge, and that any new administration, Democratic or Republican, will have a difficult time communicating with those Muscovites made deaf by their own rhetorical skills. Excessive talkativeness has been the weakest feature of Reagan foreign policy: It has apparently aggravated a Soviet bias in the same direction.