As they approach the last act of their 16-month-long peace drama, Egypt and Israel are revealing signs of opening-night jitters that, to the fainthearted, conjure visions of the whole delicately fashioned treaty coming unstuck.

In the barrage of rhetoric, charges and countercharges that have marred the past week of less than peaceful relations, there is less than meets the eye. But the symptoms of nervousness are classic:

Egyptian Prime Minister Mustafa Khalil suggested publicly that if Syria attacks Israel, Egypt might join in battle-on the Arab side. Israel fires off a note of protest, and just when the dispute seems to be petering out, Egyptian Foreign Minister Boutros Ghali says Egypt will not normalize its relations with Israel as soon as had been expected.

After another lull, Israeli Defense Minister Ezer Weizman postponed his official visit to Cairo. Ostensibly it is because of problems of keeping kosher during Passover, but Israelis dismiss the official explanation as implausible, because Weizman is not well known for his orthodoxy.

Then the Israeli frieghter Ashod, which was to have been the first Israeli ship to sail through the Suez Canal as a result of the treaty, was turned back to the port of Eilat by Egyptian maritime officials. Before Israelis could digest that news, they were being told that the planned ceremony in the Sinai to formally exchange the ratified treaties had been postponed by Egypt from April 16 to April 22.

Next, Israelis read in their newspapers that the Foreign Ministry had accused Ghali of being 'misleading,' and that Ghali was comp laining that Israeli Prime Minister Menachem Begin's pledge to continue building Jewish settlements in the West Bank will 'obstruct' the pursuit of peace.

While urging leaders of both sides to refrain from hyperbole, the influential Hebrew newspaper Haaretz calmly assured its readers in an editorial, 'There is no reason to be nervous.'

But it seems that where all else had failed, only the Passover holiday and the traditional Seder commemorating the flight of the children of Israel from Egypt managed to succeed in lowering the shrill voices.

Even then, this years' reading of the Haggadah-the ancient story of the wandering Jews-was inevitably laced in many Israeli homes with comtemporary wisecracks about Egypt's trustworthiness 3,500 years after the Exodus.

But the feeling among Israeli political leaders is that all's well that ends well, and that the rhetoriic being exchanged across the border is a natural catharsis that was to be expected on the eve of an historic moment.

Begin, having been assured by Sadat in a telephone call that all the promises made at the March 26 treaty signing in Washington and during Begin's visit to Cairo last week will be honored, is said by his aides to be serene in the belief that nothing serious is amiss.

An Israeli Foreign Ministry official observed recently that Khalil had backpeddled somewhat from his statements about Syria, conditioning the warning on Israel's refusal to negotiate with Syria.

Officials dismissed Ghali's remarks about postponing normalizing relations, pointing out that the foreign minister had been co-opted by Sadat's telephone pledge to Begin.

Moreover, there are Egyptian assurance that Islaeli ships will be able to pass through the Suez soon,and that the settlements dispute can be dealt with civilly over the negotiating table when West Bank and Gaza Strip autonomy talks begin.

As for the postponement of Weizman's trip, government officials say it would not make much sense for Weizman to begin technical negotiations in Cairo on Israil's withdrawal from the Sinai before the exchange of treaty ratification documents.

That ceremony is now scheduled to take place after Thursday's Egytian referendum on the peace treaty, which is said to explain that postponement.

"There is a feeling here to let Sadat overcome this stage of his own difficulties-internal opposition and pressures from the other Arab states. A lot of things are being said to fulfill internal needs," an Israeli official said.

"Everyone's itchy. Everyone's nervous and touchy right now. These are the first nervous moves in normalizing relations between two countries, and-I suppose they are to be expected," said a Foreign Ministry official.

Moreover, officials close to the treaty process point out that there are certain ambiguities built into the accord that would naturally lead to disputes over interpretation.

"They are calculated ambiguities, which enabled Khalil to say such things and get away with it," said a Foreign Ministry official.

For example, while Article 6 of the accord clearly states that the treaty is binding over conflicting obligations both countries have with other nations, attached minutes clearly state that "there is no assertion that this treaty prevails over other treaties..."

The Israeli view now is that with ambiguous clauses like that, it would be miraculous if last-minute disputes before the exchange of ratification did not occur between two countries that have been in a state of war for 30 years.