More than 1.8 million Bolivians went to polls today as their country sought once again to end a decade of military rule by electing a civilian government.

It was the second time in less than a year that Bolivians have been called to vote in a general election as military governments, faced with severe economic problems they do not want to deal with, have tried to transfer power to a democratically elected president and congress.

The results of the election last July were declared void because of massive vote-counting fraud, which led to one military coup in July and another in November, Bolivia has a history of political violence, election fraud and instability almost unrivaled in Latin America.

General David Padilla, Bolivia's military president, stressed last week that the armed forces are determined to gurantee a peaceful transition to civilian rule -- scheduled to take place August 6 -- and "the cleanest elections in our country's history.

Padilla also said that the armed forces recognize that "their specific duty is to maintain the security and stability of the republic, and to see this [democractization] process to completion" regardless of which of the two leading presidential candidates wins. Both leading candidates -- centrist Victor Paz Estenssoro, 71, and lettist Heran Siles Zuazo, 66 -- are former presidents.

Although the polls were late in opening in several sections in and near the capital of La Paz, including the village of Rio Seco, and ballot boxes, were reported stolen in the northern province of Beni, there were no reports of serious violence before the polling ended at 4 p.m.

Despite Padilla's assurances there was a widespread feeling here that Bolivia had entered a very unstable and potentially violent period. Such a feeling was expressed by simple campesinos, such as Rio Seco carpenter Mario Felix Puna, and by sophisticated political observers, such as La Paz journalist Ana Maria R. de Campero.

There was almost general agreement, based mostly on Bolivia's troubled, history rather than on anything specific, that is Siles appears to be winning or if there appear to be massive fraud, then a civil insurrection or another military coup -- or both -- could occur before a civilian government takes office.

"I think there will be another coup," Puna, 27, said as he waited in line to vote in the dusty courtyard of Rio Seco's only elementary school, located 1,500 feet above sea level on the Altiplano about 10 miles from La Paz.

"But this time, he said, echoing the sentiments of many other campesinos interviewed today, "if the militiary dosen't respect out vote, there will be a civil war."

Whether there will be a real civil war, like the one now ranging in Nicaragua is open to some doubt.

The peasants and workers here do not have the modern weapons possessed by Bolivia's well-equipped armed forces. Nonetheless, the campesinos here did defeat the army 27 years ago, in 1952 -- an encounter that neither the army nor the peasants have forgotten.

Most observers think there could be serious trouble if Paz, and Siles, both leaders of the 1952 revolution that led to radical changes in Bolivia's economic and social structure, cannot overcome their personal antagonism and reach a political understanding once today's votes are counted.

Although there were eight presidential candidates in this year's election, including former military presient General Hugo Banzer, it was expected that Paz and Siles would be the frontrunners but that neither would get an absolute majority of the vote.

In that case, the selection of the president would be left to the Congress, also elected today. Siles has threatened that if he won a plurality of the vote but lost to Paz in the Congress, then he would mobilize his supporters among the students, peasants and workers.

Complicating the situation further is the fact that military leaders detest Siles because they blame him for their defeat in 1952. And the citizens of Santa Cruz, a booming oil and natural gas center in the eastern lowlands, refuse to even allow Siles to enter the city because of an incident during his presidency [1956-1960] when seven students were tortured and killed by government troops.

There is much speculation among persons of various political views in La Paz that some segments of the military despite Padilla, might attempt a coup if it appeared that Siles were going to win office. Santa Cruz, meanwhile, might mount a serious insurrection possibly with the help of troops garrisoned there -- if a Siles victory seemed likely.

Although Siles is now considered to be far to the left of Paz in terms of style and because of Sile's alliance with the Leftist Revoluntionary Movement, both candidates said during their campaigns that Bolivia must quickly reestablish its foreign credit by imposing austerity measures that will be painful but necessary.

If based on partial and unofficial returns that will be available beginning "monday, Siles and Paz can quickly reach an understanding, most observers believe an relatively smooth transition can occur. But if the two old allied cannot reach an accord a political upheaval could result. CAPTION: Picture, VICTOR PAZ ESTENSSORO . . . presidential candidate