Washington — Trying to determine the future of US-Soviet relations is a hazardous business. But as they look at the eight-month period leading up to the US presidential election, a top negotiator, a United States senator just returned from Moscow, and a number of independent analysts see:
* An improvement in what the diplomats call the ''atmospherics'' of the relationship.
* Some forward movement on peripheral issues, such as proposed improvements in the Washington-Moscow communications hot line.
* A return to the strategic nuclear arms reduction, or START, talks. There is , however, no guarantee of progress in the START negotiations, and most experts doubt that the Soviets will return to the parallel talks on intermediate-range forces (INF) in Europe.
In other words, the outlook would be for no immediate breakthroughs but slow, painful, and possibly glacial progress.
In order to break the ice, some State Department officials favor what Newsweek magazine has called a ''shortcut deal'' - an interim nuclear arms control agreement based on ''agreeable elements'' of the unratified SALT II treaty. But this idea is opposed by high-level Defense Department officials.
The top US negotiator, Edward Rowny, is skeptical of this approach and said in an interview last week that the US should not propose it. Even if it were agreed upon here, the approach might prove difficult for the Soviets to accept.
Some White House officials say they think a summit meeting between President Reagan and Soviet leader Konstantin Chernenko would be a good way to give the relationship a new boost. But a number of experts in the administration maintain that a summit without careful preparation and guaranteed accomplishments would be risky, in part because it would raise public expectations to an unrealistic high. Some of the experts fear White House advisers are looking for preelection political gains from a summit and are not giving enough attention to possible drawbacks.
But outside the now suspended nuclear arms control negotiations, administration experts see some room for progress in improving communications between the two sides, introducing so-called confidence building measures, renewing cultural exchanges, and moving toward a ban on chemical weapons. The US is considering a new proposal to be made at the talks on conventional, or nonnuclear, weapons set to reopen March 16.
And Sen. William S. Cohen, a Maine Republican, who returned from a trip to Moscow last week, says that Soviet experts and political leaders have shown interest in the ''build-down'' proposal that was endorsed last year by President Reagan and which the US introduced during the most recent round of the START talks.
Mr. Cohen is one of the leaders of a congressional coalition sponsoring the new concept, which is designed to reduce ballistic missile warheads by one-third on each side with particular emphasis on eliminating what are considered to be the most ''destabilizing'' nuclear weapons. Under the build-down principle, no new weapons should be deployed unless a larger number of existing weapons are destroyed.
Cohen said in a telephone interview that the Soviets apparently did not show interest in the build-down concept when it was presented to them by Lt. General Edward L. Rowny, the START negotiator, because at that time, they were focusing on the INF negotiations and on their opposition to the deployment of American Pershing II missiles in Europe. The senator said that in Moscow Soviet scientists began asking for the first time about the details of the build-down proposal.
The senator said it was now clear that the Soviets would not return to the INF talks but that they would probably return to START and bring INF issues into those talks. Under those circumstances, Cohen said there was some reason for cautious optimism but no reason to raise expectations very high.
General Rowny said the Soviets had injected a new element into the 40-nation Geneva conference on disarmament by suggesting recently that they might agree to ''continuous'' on-site verification of the destruction of chemical weapons. He said that translators were now working to determine precisely what the Soviets meant by this suggestion. But other officials warn that many other complicated elements would have to fall into place before the US and Soviets could come to a final agreement on chemical weapons.
An administration official said, meanwhile, that the US was considering making a new proposal at the East-West talks on conventional forces in Europe, which will reopen soon in Vienna. The new proposal might allow for an agreement in principle to be reached before the two sides resolved the so-called data-base question. This has been one of the main issues in the talks between the NATO allies and Warsaw Pact nations in the now 10-year-old negotiations.
The Soviets have claimed that the opposing conventional forces in Central Europe are roughly equal. The West argues the Soviets enjoy superiority in troop strength. Given these differing data-base starting points, it has been difficult to get the talks moving. But State Department officials say the Soviets' latest proposal offers some hope.