Secretary of State George P. Shultz leaves for Geneva this morning to work out final details of the intermediate-range nuclear forces (INF) treaty, explore new Soviet hints about troop withdrawals from Afghanistan and prepare the way for the U.S.-Soviet summit meeting in Washington scheduled to begin in a little more than two weeks.

Shultz was described as optimistic that he and Soviet Foreign Minister Eduard Shevardnadze will be able to resolve outstanding INF issues, which were described by a U.S. official as about 30 in number, of which perhaps five are significant.

A senior State Department official said the chances are "about 99 out of 100" for resolution of these last few INF issues, which mainly concern ways to monitor and verify compliance with the pact. But other State Department officials said it is by no means certain that Shultz and Shevardnadze will be able to announce after the end of their two-day talks Tuesday that all questions have been solved, so that the treaty can be signed by President Reagan and Soviet leader Mikhail Gorbachev during their Dec. 8-10 meetings here.

The main issues remaining, according to U.S. sources, involve:

Data about the location of existing medium- and shorter-range nuclear missiles. The United States has asked the Soviets to provide additional detailed information about the location of these missiles, which are to be eliminated by the proposed pact.

Verification and inspection of Soviet SS25 missile plants and sites. The SS25 is a long-range weapon not covered by the INF treaty but it is difficult to distinguish from the SS20, a medium-range missile that is covered.

In a precedent-setting step, the Soviets last week agreed to allow the United States to conduct on-site monitoring of the Soviet final assembly plant for SS25s, in order to insure that look-alike SS20s are not being produced there. Some details of this agreement remain to be worked out, including the Soviet insistence on monitoring a U.S. plant of "comparable value" in return.

In addition, sources said, there is disagreement on the U.S. demand for spot inspections of SS25 operating bases and other facilities to make sure SS20s are not present, and on a broader U.S. demand for other spot inspections. Certain procedural issues about the nature and timeliness of inspection are also not yet agreed.

These final issues and details are being discussed against the deadline of the coming summit, a pressure-cooker process that drew objections Friday from departing Pentagon arms control chief Frank J. Gaffney Jr., who was ousted by Frank C. Carlucci, the newly confirmed secretary of defense. Gaffney said he had told Reagan in a resignation letter that the INF negotiations against a deadline have created "a very dangerous situation."

Aides said Shultz is hoping to concentrate with Shevardnadze on laying the groundwork for progress at the summit on the 50 percent cuts in strategic, or long-range, nuclear arsenals that both sides say they want. But some officials expect the more-urgent INF issues to crowd out this discussion.

Hints of a Soviet move toward withdrawal of its 115,000 troops from Afghanistan are also high on Shultz's list for exploration with Shevardnadze. The hints came last week in a Geneva meeting of Undersecretary of State Michael H. Armacost and Soviet Deputy Foreign Minister Yuli Vorontsov and in other forums.

Vorontsov told Armacost, according to State Department officials, that a new round of the U.N.-sponsored indirect talks on Afghanistan should be held in February or before and that this should be the last one necessary in the 5-year-old series.

Vorontsov did not provide a timetable for withdrawal of the Soviet troops, something that the United States has continued to demand in public and private statements. Soviet Foreign Ministry spokesman Gennadi Gerasimov said in Munich last Monday that a pullout could take place in seven to 12 months if agreement can be reached on the composition of a post-withdrawal Afghan government. But no such proposal has been made officially.

The U.S. position is that a Soviet withdrawal schedule should come first and that it might well contribute to agreement among the Afghan parties about an interim government. Much the same sequence is being proposed by U.N. Undersecretary General Diego Cordovez, chief U.N. negotiator on Afghanistan.

Cordovez, who was in Washington Friday for an unannounced meeting with Armacost, welcomed the Soviet call for another round of indirect talks between Pakistan and the Soviet-backed Afghan government. But Cordovez said he does not intend to convene such a meeting until it is clear that accord can be reached on the length of the Soviet withdrawal timetable.

The U.N. mediator plans to visit Pakistan and Afghanistan next month in an attempt to move the diplomatic process forward.

A senior State Department official said yesterday the department has heard "rumors" that a Soviet announcement about Afghanistan will be made at the Dec. 8-10 Washington summit but that no confirmation of this has been received. "We're continuing to press them to start getting their troops out," the official said.

Pakistan President Zia ul-Haq said in an interview published yesterday in Vienna that "the Afghanistan theme at the summit between Reagan and Gorbachev will decide the future of relations between the two superpowers." He said, "It seems that the Soviets are serious in their offer to withdraw their troops from Afghanistan . . . but they fear this would result in a massacre of their supporters there."

Other officials who have been watching the Afghan situation noted that the Soviets have been saying since shortly before the 1985 Geneva summit that they "want to get out" of Afghanistan and that for most of this year they have also been saying "the decision has been taken" to get out. Nevertheless, there has been no announcement of a timetable for withdrawal or orders to the Soviet forces to withdraw. For several weeks, an official said, the Soviets have been making "new noises" about Afghanistan through a great variety of channels in eastern and western Europe and Afghanistan. The officials said it is unclear whether the new hints are intended to create a better political climate for Gorbachev's trip to Washington or whether they are the beginning of a new phase of Soviet policy in Afghanistan.