FOR a man who has succeeded in shaping this week's Middle East peace conference almost exactly to his liking, Israeli Premier Yitzhak Shamir is going to the talks with a marked lack of enthusiasm.His aides say they fear that Israel's major foe, Syria, is not prepared to offer a full peace treaty even if Israel were to make concessions on the disputed Golan Heights. They also worry that the Jewish state will come under heavy international pressure to withdraw from the occupied territories, a step Mr. Shamir has vowed never to take. But the Israelis have ensured themselves considerable protection in the structure of the peace talks. The upcoming negotiations are "the culmination of our diplomatic efforts and political initiative of 1989," one senior Israeli official claimed last week. During the eight months of US Secretary of State James Baker III's efforts to convene the talks, the Israelis have managed to fight off all attempts to convene a full international conference with United Nations participation, as the Arab side always demanded. Instead, Israel has been guaranteed the direct, bilateral negotiations with its neighbors that it insisted on, and that imply recognition by the Arabs of the Jewish state's existence. It has also won assurances that the opening session in Madrid will be largely ceremonial, with no power to reconvene, vote, or impose solutions on the parties. The talks will also follow the "twin track" approach to solving Israel's disputes with the Palestinians and with the Arab states in parallel, as Israel proposed in 1 989. On an official level, Israel has also prevailed in its refusal to sit down at the table with the Palestine Liberation Organization (PLO). None of the Palestinian delegates in the conference room will be formally linked to the PLO. The pretense that the PLO is not involved in the conference is wearing increasingly thin, however. PLO headquarters in Tunis chose the Palestinian delegation, and a number of leading Palestinians unacceptable to Israel have been invited to the talks as "advisers" who will be allowed into the conference center, if not the negotiating room itself. The Palestinians are likely to pose the first dilemma for the Israeli delegation by demanding a freeze on Jewish settlements in the occupied territories for the duration of the peace talks. Though the Israeli government has firmly ruled out such a move, it may be pressured to give way, not only by its Arab negotiating partners, but also by the United States and the Soviet Union, cosponsors of the conference. Israeli officials are tight lipped about how they would handle such a challenge, as they are about every detail of their negotiating strategy. Shamir, whose decision to lead the delegation personally indicates his intention of keeping iron control over the negotiations, "is playing his cards extremely close to his chest," says Hebrew University politics professor Gabriel Sheffer. Shamir's move has prompted reports that Foreign Minister David Levy is considering resigning over his ministry's virtual exclusion from talks' preparations. The prime minister has named two close advisers to accompany him to the talks - his chief of staff Yossi Ben Aharon, who will conduct bilateral discussions with Syria, and cabinet secretary Elyakim Rubinstein who will handle talks with the Jordanian-Palestinian team. That Shamir is taking two of his best men to the talks "may be a clue that the Israeli government is preparing for some serious negotiations," suggests Dr. Sheffer. "Rubinstein is working hard on ideas for autonomy" adds a source familiar with the cabinet secretary's work. Israeli officials are angry, though, at what one senior source called Syria's efforts to "disintegrate whatever grouping exists of countries ready to participate in multilateral negotiations" among several Arab countries and Israel about regional issues such as arms control, water use, and environmental questions. Syria has said it will not join such talks until Israel has agreed to hand back the Golan Heights. Although Israel has always put highest priority on direct bilateral peace talks with its enemies, the government is also anxious to join regional negotiations with its neighbors as a way of inserting Israel into a region which has never recognized its existence.