Shehu Usman Aliyu Shagari, Nigeria's first civilian president in 13 years, is an austere man who evinces a shy manner and called himself "the reluctant candidate" during his election campaign.

Both critics and admirers characterize him as stringent on matters of propriety and "clean" of any taint of corruption. A slight man who perpetually wears tinted eyeglasses, Shagari is a devout Moslem who bears the honorary religious title of "alhaji," signifying that he has made the pilgrimage to mecca.

Born in 1924 of a humble farming family in the northwestern Nigerian village of Yabo, Shagari is a Fulani, from a nomadic group of cattle herders who conquered the Hausa of northern Nigeria at the beginning of the 19th century.

He holds two college degrees in education and worked as a teacher and primary school headmaster through the early 1950s. He was secretary of the Northern People's Congress (the predecessor of his National Party of Nigeria) from 1951 to 1956 and was an elected member of the Nigerian parliament until the country's first military coup in January 1966.

After the coup and during the Nigerian civil war, Shagari lived in his native Sokoto state with his wife and six children until asked to join the military government of Gen. Yakubu Gowon as federal commissioner of finance, succeeding his present political nemesis, Obafemi Awolowo. He served as federal finance commissioner from 1971 to 1975.

When Gowon was overthrown in a bloodless palace coup in 1975, Shagari was appointed to the largely ceremonial chairmanship of Peugeot Automobile Nigeria Ltd. by the military government of retired Gen. Olusegun Obasanjo.

Shagari became one of the founding members of the National Party of Nieria and a prsidential candidate shortly after the military lifted the ban on political activity in September 1978.

Politicians who know him say Shagari sees himself as an evenhanded conciliator and healer, attributes he hopes to use to thwart any degeneration into the political chaos that destroyed Nigeria's first civilian government.

Even his rhetoric is subdued. When Awolowo challenged the legitimacy of his election win, Shagari called the move "unsportsmanlike."

Shagari's critics perceive him as dull and lacking forceful leadership qualities. Shagari responded to the criticism in a New Year's Day speech without referring to his critics directly.

"I do not believe in playing to the gallery for the achievement of cheap popularity all in the name of dynamism," he said.

"When you talk to him," said a knowledgeable Nigerian, "you know immediately if he is interested in what you are saying." If Shagari just nods his head and does not respond, the source said, then he is just waiting for you to finish and leave. "If he starts asking questions, then you know you have his ear," he said.

The recent appointment of his 23-member Cabinet is an example of how Shagari will work, said a well-known Nigerian businessman. Ninety percent of the Cabinet "are unknown men in tahis country but are capable intellectuals and they are all beholden to Shagari", he said.

"He keeps his thoughts close to his vest," said a Nigerian newspaper official. "Even his close adviser won't know which way he is headed until he made up his mind."

One area of specualtion about Shagari has been whether the soft-spoken president will be as tough and adament as the military government is on foreign policy issues, such as the August nationalization of British Petroleum's Nigerian interests after charges that they were selling Nigerian oil to South Africa. The military government abhored South Africa's racial apartheid system of segregaation.

In a breif September interview, Shagari said "I've always been an ardent supporter of" the military government's foreign policy. "My administration will pursue this [policy] and intensify it."

During a trip to Monrovia, Liberia, in early December -- Shagari's first outside Nigeria since taking office Oct. 1 -- the Nigerian president participated in a five-country conference on the fighting in Western Sahara. The conference was hosted by Liberian president William Tolbert,current Organization of African Unity chairman. Shagari joined the unanimous request to Morocco to withdraw its troops from the Western Sahara and allow the future of the former Spanish colony to be decided by a U.N.-supervised referendum.

"That was to be expected," said one Nigerian who accompanied Shagari on the Monrovia trip. "But more importantly I got the impression from the things he said that he is going to be tougher, more radical on foreign policy matters than the military government was. That was a surprise."