PRESIDENT REAGAN HAS spoken hopefully about the prospects of an improved relationship with Moscow -- an early summit, for instance, and progress in arms reductions -- now that Mikhail Gorbachev is in power. In the new Soviet leadership's own initial signals, however, a bit more of a hedge is evident.

Take the summit. It's a good idea. The coincidence of Mr. Reagan's reelection and Mr. Gorbachev's elevation makes this a reasonable moment to resume a political ritual with its own special combination of opportunity and risk. No major breakthrough could be expected, but it would be enough to pursue the modest purpose stated by Secretary of State George Shultz -- "to review the bidding and see where we may go from here."

Somewhat to the administration's embarrassment, however, Mr. Gorbachev still has not accepted the Reagan invitation. He is "studying" it. The pause suggests a certain element of deliberation that was evident in a couple of other things that have happened in the Soviet leader's first days in power.

He -- who else? -- saw to it that a little extra threat was transmitted to Washington. Dusko Doder, chief of this newspaper's Moscow bureau, has reported that the new Soviet leader sternly warned Pakistan to halt its support of the Afghan rebels, lest Moscow stir dissident tribesmen inside Pakistan. That much was expected and had happened before; the Pakistanis are standing their ground. But meanwhile, other Soviet sources conveyed to Mr. Doder that Moscow might similarly promote destabilization in Pakistan if the United States took military action against Nicaragua. This hint of linkage came in a form that could be, and soon was, officially denied. Is that to be the Gorbachev style?

In a similarly ambiguous manner, the Kremlin let loose a propaganda blast, delivered by the chief Soviet negotiator, about arms control. In substance it came down to the familiar complaint -- which appears to be true -- that the United States wants to keep its "Star Wars" deployment options open. In form, however, the blast raised the question of whether the Soviet negotiator compromised the pledge of confidentiality the two sides took as they opened talks in Geneva. The answer apparently hinges on exactly when the Soviet statement was recorded.

You could say it is a small matter, but at this point in the Soviet-American proceedings, small matters are the subject of much attention. The two sides are feeling each other out. The tone is being set for a phase of Soviet-American relations that both sides realize is exceptionally important. It is a moment for the closest attention to "signals," sent and received.