Four months after President Reagan met Soviet leader Mikhail Gorbachev at the summit in Geneva, U.S.-Soviet relations are suffering from a case of the blahs.

There is increasing doubt that a major arms control agreement is in the making, even an accord limited to intermediate-range nuclear forces (INF) in Europe. Though Gorbachev made surprising and seemingly sweeping proposals in January to phase out all nuclear weapons by the end of the century, his offer led to no new Soviet flexibility in the subsequent round of Geneva negotiations, according to U.S. officials.

In response to Gorbachev, the Reagan administration introduced new, more explicit and difficult conditions for agreements, including on-site inspection requirements that the Kremlin is unlikely to accept.

The Soviets have mounted a sustained diplomatic and propaganda offensive on behalf of a total ban on underground nuclear tests that has generated irritation in official Washington, where it is considered a "phony" issue by the administration. The United States demonstrated its disdain for Moscow's proposal yesterday with an underground nuclear test in Nevada, a move that may cause the Soviets to abandon their self-imposed moratorium.

Both sides have called for a meeting of U.S. and Soviet nuclear testing experts next month, but the terms of the invitations are so different that such a conference appears unlikely. What is now in the offing, instead, is a well-publicized U.S. underground test the third week of April at which Washington will lament the absence of invited Soviet observers.

The timing and agenda for the next Reagan-Gorbachev summit meeting remain unsettled, though the two agreed in Geneva to meet again. The Soviets have not replied to a Reagan message last December that proposed a summit in Washington this June. Even high-level U.S.-Soviet discussions to begin preparations for a summit have not been scheduled. Eduard Shevardnadze, the Soviet foreign minister, has ignored or passed up American invitations to begin discussing the summit in January and again this month. "It's now up to them," said an administration official in a tone of exasperation.

Yet American officials report that the Soviets continue to repeat that Gorbachev is committed to holding another meeting with Reagan at some point. This was said clearly by Soviet Premier Nicholai Ryzhkov to Secretary of State George P. Shultz last weekend in Stockholm, according to the United States.

Both sides want the results of the next summit meeting to be "important," Shultz said in testimony before a Senate Appropriations subcommittee Wednesday, but added that "I have to say that progress since Geneva has been disappointing."

American officials now hope that some breakthrough may be possible when departing Soviet Ambassador Anatoliy Dobrynin returns to Washington to begin paying farewell calls here. State Department sources said they expect a Shultz-Dobrynin meeting shortly after Shultz returns from his current European trip March 30, and are hoping for word from Dobrynin then about at least preliminary meetings toward a 1986 summit.

Officials here are intrigued by Dobrynin's new job as a secretary of the Communist Party Central Committee. This is a senior post in the Soviet leadership, but Dobrynin's precise responsibilities have not been explained. He is to be involved in foreign affairs, but it is not clear whether he will work on East-West relations.

While summit planning is in abeyance, Soviet-American relations putter along. There are both positive and negative signs in the diplomatic tea leaves: Pluses

* Bilateral relations are making "modest progress," according to U.S. sources. Pan American World Airways and Aeroflot will resume commercial air travel between the two countries next month. Consulates in New York and Kiev, which are to be staffed with about 30 officials each, could open this summer. "People to people" exchanges sponsored by Reagan and endorsed at the summit are moving ahead.

* A new round of consultations by senior diplomats on Third World flashpoints has begun. The first, on Southern Africa in Geneva March 6, didn't accomplish much in the U.S. view, but the dialogue is welcome. The Soviets proposed a next meeting on Afghanistan issues later this month, but Washington would like this topic to be discussed at the Shultz-Shevardnadze level first.

* Some movement on human rights issues in the Soviet Union, including the release of Anatoly Shcharansky, the medical-related travels abroad of Yelena Bonner (wife of Nobel laureate Andrei Sakharov) and approval for about 40 members of divided families to emigrate to the United States, close to one-fifth of those on the U.S. divided-family list.

* A "good first meeting, with very little polemics" on the subject of preventing proliferation of chemical weapons held March 5-6 by U.S. and Soviet diplomats in Bern, Switzerland. Like the other topics above, the chemical-weapons discussions were given impetus by agreements at last November's summit. Minuses

* The U.S. order presented March 7 that the Soviet Mission to the United Nations must be reduced from 275 to 170 officials in two years. The basic administration decision to demand the cuts, intended to diminish Soviet espionage activity in New York, was made last September, with its implementation delayed until the end of the Soviet Party Congress. The Soviets have protested vigorously. But Premier Ryzhkov did not mention the issue in last weekend's meeting with Shultz, U.S. officials said.

* The probe by U.S. warships into Soviet territorial waters March 13 to gather intelligence and test Soviet defenses. The Soviets protested the incident, calling it "clearly provocative," but the Pentagon said the U.S. ships were exercising "the right of innocent passage."

* Reagan's harsh anti-Soviet rhetoric in recent televised speeches justifying his $320 billion military budget request and his request for $100 million in U.S. aid to anticommunist rebels in Nicaragua. Reagan used similar anti-Soviet arguments in speeches in earlier years on the same topics, but that was before the Geneva summit, hailed as "a new start" on U.S.-Soviet relations.

The Nuclear and Space Arms Talks in Geneva are central to the prospects for major improvement in the Washington-Moscow relationship, according to both sides, and it is here that unhappiness in both capitals is strongest.

The view in the Kremlin, as expressed Feb. 6 by Gorbachev to Sen. Edward M. Kennedy (D-Mass.), is that the Reagan administration has no serious intention of reaching an arms control agreement. Gorbachev told Kennedy, according to an account of their meeting, that he had made the Jan. 15 arms offers to demonstrate to the world that the Soviet side is serious, even if Washington is not.

Reagan, who initially said he was "grateful" for the Jan. 15 proposals, decided in late February to respond by testing Gorbachev's intentions in vigorous fashion.

An intimate discussion by Reagan and a few top advisers aboard Air Force One while flying to and from Grenada Feb. 20 resulted in a presidential decision to propose that all U.S. and Soviet intermediate-range missiles worldwide be eliminated within three years, two years ahead of the somewhat visionary schedule for elimination of European INF missiles proposed by Gorbachev. Administration sources said the three-year timetable for a "zero-zero" INF plan had not been recommended to the president by any of his advisers, but seems to have been Reagan's personal, spur-of-the-moment contribution.

The decision to promptly table a specific proposal for verification of an INF treaty also emerged from the airborne policymaking session, sources said. The proposal submitted early this month that U.S. inspectors be allowed on-site to count Soviet missiles and monitor Soviet military production was not likely to be accepted, administration officials acknowledged, but was intended to "smoke out" the Soviet position in light of statements by Gorbachev and others recognizing the importance of verification.

The next round of the Geneva negotiations is scheduled to begin May 8. Before then, Reagan is expected to decide whether to continue observing the terms of the unratified 1979 SALT II strategic arms treaty by taking two more U.S. Poseidon nuclear submarines out of service to make room for a new Trident submarine's 24 missiles. If the Poseidons are not demolished, the Trident will put the United States over the SALT II limits.

The SALT II decision, and the renewal of testing by the United States, will help establish a new climate for the next phase of the superpower relationship.