Gaza Mayor Rashid Shawa said yesterday that Israel has started withdrawing from the occupied Gaza Strip with the purpose of unilaterally implementing limited autonomy here as an experiment.

However, Shawa and other Arab officials are unhappy about the perceived Israeli move.

Its real aim, they believe, is to stire renewed Palestinian unrest in the narrow, densely populated strip so that the experiment will be a demonstrable failure. Then, the officials fear permanent reoccupation will become palatable to international opinion, including that in Europe.

An Israeli spokesman said that there is no such "premeditated policy" but that the government favors allowing Gaza inhabitants to take over whatever they could handle.

But Shawa said in an interview, "I think they are unilaterally withdrawing now. There are signs of it everywhere, but we are not pleased as you might think we should be. This is a two-edged sword, and I think they are looking for a justification to make the occupation permanent."

He said he has been informed by the military governor in Gaza that 100 of the 150 Israeli civilian officials who work in the military administration of the strip will leave in the next three to four months and that the remainder will be gradually phased out.

Moreover, Shawa said, an Israeli staff officer assigned to oversee a key governmental department, the Interior Office, has been replaced by an Arab director general to coordinate the affairs of the various municipalities in the Gaza Strip. Shawa said he has instructed municipal heads not to cooperate with the new Arab director general.

Shawa said his suspicions were confirmed last week when he was visited by former foreign minister Moshe Dayan. He said Dayan asked him what the reaction in the Gaza Strip would be if Israel unilaterally declared autonomy within three months.

While Dayan stressed that his visit was a private one, Shawa said, the former foreign ministed noted that the Israeli government has come under mounting pressure from the European Common Market countries to take some steps toward Palestinian self-determination.

Before resigning as foreign minister in a policy dispute with Prime Minister Menachem Begin last year, Dayan frequently advocated a unilateral withdrawal of Israeli forces from the West Bank and Gaza Strip as a way of extricating Israel from the mire of 13 years of occupation and at the same time giving some momentum to the moribund autonomy negotiations.

With varying degrees of enthusiasm, the unilateral withdrawal theme has been picked up by some members of Begin's government and the parliament but has never been officially debated, much less endorsed. However, the so-called "Gaza first" plan, in which limited autonomy would be implemented in the Gaza Strip first as a model for the West Bank after an Egyptian-Israeli agreement, has received much attention by the Cabinet and was endorsed by Begin in a meeting with Egyptian President Anwar Sadat last January in Aswan.

In denying Shawa's remarks, Begin's spokesman, Dan Pattir, said, "I don't think it's a premeditated policy. If the local indigenous elements can run things without stirring up trouble, then the tendency is to let them take over what they can. But this isn't a question of unilateral withdrawal in the sense that he [Shawa] speaks."

There was no discernible evidence in the Gaza Strip yesterday that the number of Israeli Army troops had been reduced. Shawa said he expected the soldiers would be the last to be withdrawn, probably to Army bases just inside Israel proper.

The number of Israeli troops here is a closely guarded secret, and it is impossible to tell by observation whether any garrisoned troops have been pulled back because they are visible mostly in small patrols of three of four soldiers.

Shawa said if the soldiers are withdrawn, "there would be chaos, and frankly I think they [The Israelis] are very keen on creating chaos."

"We are not ready for withdrawal. We have no police, and before long the people will be fighting each other," Shawa said. He said the local police force of about 110 Arabs is so meager that most of it is tied up in headquarters handling administration, leaving only a handful available for traffic duty and patrols.

"It is only because of the Israeli soldiers running around here that people behave. I know it sounds funny to say it, but we are very worried about this withdrawal," Shawa said.

The paradox was magnified when Shawa disclosed he had "sent word to our friends outside," meaning the Palestine Liberation Organization, warning of the danger of an Israeli withdrawal now and spelling out his suspicions of the motive.

Bethlehem Mayor Elias Freij, who was also visited by Dayan, said he shared Shawa's concern.

"It's a dilemma," Freij said. "Can we ask them not to withdraw? Of course, not, but with our pitifully small police force, we cannot protect ourselves.They will create chaos. They want to put us in a boiling pot, and maybe they will make stew out of us."

Both mayors said they want a total Israeli withdrawal from the West Bank and Gaza, but only on the basis of permanent independence with a governmental infrastructure prepared in advance with the PLO and, perhaps, involving links to Jordan. Unilaterally imposing autonomy before then, the mayors said, would undermine the chance of permanent self-determination and present the Israelis with a pretext for institutionalizing the occupation.

Morover, Shawa charged that "Gaza first" plan was designed to isolate the Gaza Strip from the West Bank and weaken Palestinian unity, as well as avoid having connecting Gaza and the West Bank. Such a corridor would probably be necessary to entice Jordan, which has no access to Mediterranean Ports.

Despite Shawa's assertion of the inseparability of the West Bank and Gaza, there are striking differences between the two areas that would appear to enhance the prospects here for a peaceful transition from occupation to self-government, if it were given a chance. Most of the 450,000 Arabs who live in this crowded, 25-mile-long strip of sand dunes that juts along the Mediterranean are Palestinian refuges who came here in 1948 of their offspring.

But because they lived under Egyptian rule between 1948 and 1967, they naturally developed an identitity with Egypt that has not disappeared under 13 years of Israeli occupation.

Many of the strip's bureaucrats, businessmen, teachers and landowners have studied in Egypt and learned Egyptian methods of commerce and government.

While there is a vocal Palestinian national movement here, it has been softened by the strip's ties to Egypt and by an economic and social revolution that has not occurred in the West Bank.

Unemployment in the strip is practically nonexistent, while 10 years ago 60 percent of the population was dependent on U.N. welfare.