SANTIAGO, CHILE -- Tensions appear to be growing in Chile's military government over whether President Augusto Pinochet is the right man to lead the limited restoration of democracy planned for the end of the decade.

In less than 18 months, the four-man military junta must decide whether to nominate Pinochet for another eight-year term when his current period in office ends in March 1989. The junta must agree unanimously on a candidate under the regime's plan for a plebiscite and congressional elections in late 1988 or early 1989.

Since early June of this year, however, all but the Army member of the junta have said openly they would prefer a civilian president.

The Army's representative, former chief of the secret police Gen. Humberto Gordon, supports Pinochet for another term. But he is thought to believe that the president should separate his fortunes from the Army and resign as its commander-in-chief before becoming a candidate.

There were hints last year of friction in the junta over the succession, but these died down when the military closed ranks around Pinochet after leftist guerrillas ambushed his motorcade in an unsuccessful assassination attempt in September.

The resurgence of concern appears to have been prompted by recent evidence that Pinochet was about to launch a full-scale campaign for the presidency.

On July 7, Pinochet reshuffled his Cabinet, in what was generally seen as an attempt to rebuild confidence among former supporters. Many of them, alarmed by the danger of polarization since the opposition united with a wave of protest demonstrations in 1983, have become disillusioned about the pace of the military's promised transition to civilian rule.

The majority of the opposition, meanwhile, has begun a campaign for free elections to replace the military's program which calls for a plebiscite to confirm or veto the junta's presidential nominee.

The opposition campaign includes a call on voters to register in massive numbers and vote against the junta's candidate in the plebiscite if free elections are not obtained.

Under the military government's constitution, the junta must unanimously nominate its presidential choice by December 1988, with the plebiscite being held by Feb. 11, 1989.

If the junta's candidate loses, Pinochet would remain in power until March 1990, when competitive presidential elections would be held in which Pinochet could run.

The campaign for free elections is supported by the country's largest party, the centrist Christian Democrats, and by socialist groups. But it is opposed by the Communist Party, a significant political force, which argues that a genuine election is impossible under Pinochet and supports the use of guerrilla violence against him.

The first public sign of renewed disquiet in the junta over general Pinochet's future came in an interview with the British Broadcasting Corp. and The Economist magazine in June by the Navy's commander-in-chief, Adm. Jose Toribio Merino.

"I don't think Pinochet will present himself as a candidate or be asked to be voted as a candidate," the admiral said, adding that the next president should be a center-right civilian in his early 50s. Pinochet is 71.

Merino's remarks contradicted calls by some government officials and high-ranking Army officers for Pinochet's nomination. But Merino was backed by the Air Force commander, Gen. Fernando Matthei, and the chief of the national police, Gen. Rodolfo Stange. Both men insisted that the military must play no role in electing the next president beyond fulfilling its duty under the constitution it drafted to name the candidate.

The signs of discontent within the junta followed indications that Pinochet's supporters were launching a campaign for him to become the presidential nominee. Pro-Pinochet slogans and glossy new posters of him and his wife have appeared on the president's increasingly frequent provincial tours. There were promises of stepped-up housing programs for the poor, and the opposition press publicized a leaked "civic action plan" instructing local authorities on how to use their resources for the "projection of the regime."

Pinochet appears to have no doubts that he should be the candidate and should run as Army commander-in-chief with the military's full institutional backing. He recently declared that he can already count on 40 percent popular support, against independent polls that give the junta less thatn 20 percent and Pinochet much less.

Sources close to the military reported growing skepticism over Pinochet's claim, leading to fears that the military might be dragged down with him to a political defeat that would leave the armed forces vulnerable to pressure for reform and trials of officers accused of human rights abuses.