Bill Brock pauses before answering a question in his soft, almost whispery Tennessee drawl. He cleans out his pipe with the flick of a pen, then lights the pipe and takes a puff, tilting his head back reflectively. A larger-than-life painting of President Teddy Roosevelt hangs prominently behind his desk.

"I happen to think he was one of our great presidents," Brock says. "I like the way he operated. 'Walk softly and carry a big stick' is the posture I think this country should have."

That's the same posture U.S. Trade Representative Bill Brock would like to have. Brock, former chairman of the Republican National Committee who nearly was ousted from that job last summer, already has quietly taken a leading role in the drama surrounding the politically sensitive Japanese auto imports question, won victories against his cabinet competitors and entrenched himself in the good graces of President Reagan and Congress.

Brock -- who lost his reelection bid for the Senate five years ago and nearly was passed over for the chairmanship of his party because he was considered a loser -- has bounced back. The man who was quick with the caustic grip several months ago not only walks softly now, but speaks softly. He said he has chosen to work with his opponents rather than fight them and has put his political skills to good use.

For example, several weeks ago when Secretary of State Alexander M. Haig Jr. reportedly was after a leading role in discussions with the Japanese on the import car issue, Brock was silent. But within several days his spokesman announced that the president has reassured Brock that any trade discussions would be led by the trade representative's office.

Several days later, Sen. Bob Dole (R-Kan.) and other members of the Senate Finance Committee were reassuring Brock, a former colleague on the Finance Committee, that the trade policy area was his and not the State Department's.

"The committee supports him very strongly," a committee staffer said. "And of course," he was a member of the Finance Committee, and there's more support than usual."

During the Japanese auto discussions, Brock "didn't move out quickly with a public line," said Robert B. Hormats, assistant secretary of state for economic affairs. "He talked to all the actors. It's given him a lot of credibility on the issue."

Brock, discussing the role after three months in office, said that confusion reigned within and outside the new administration on the auto issue. Reagan decided, after his cabinet publicly aired its internal divisions, to allow the Japanese to restrict imports of their cars here voluntarily, if they see it in their interest to do so.

"All of us were new," Brock said. "The Japanese weren't sure who to deal with" in the administration. "They started dealing with everyone and got confused . . . . We have to speak with one voice." But the administration spoke with many voices, Brock said.

Persons within the administration didn't even know with which Japanese leaders the issue should be discussed, Brock continued. "We didn't know who to talk to there," he said. "It seemed as though there were two different individuals speaking for Japan. Both sides were having trouble adjusting to the new administration." Brock wouldn't say who the two individuals were, but sources said the two Japanese camps in conflict were the Ministry of International Trade and Industry and the Foreign Ministry.

The Japanese "wanted to see everybody to find out what we were doing," Brock said. But every person in the administration with whom they talked put their own slant on the issue, Brock said.

In addition, Brock said the U.S. auto companies, while demanding auto import restrictions to improve their own sales, "were issuing pretty optimistic sales forecasts for 1982." The Japanese concluded that they didn't need to restrict sales of their cars here if American car sales were expected to take off.

Also, it seemed ironic that Detroit complained about $4.5 billion in losses last year and inadequate cash flow to make plant improvements "when they're still paying bonuses, dividends," Brock said. "That was confusing."

Brock said the administration didn't ask the United Auto Workers union or the heads of the major auto companies to hold down wage demands, cut salaries, stop paying dividends or make other concessions to help themselves because the administration felt it was best to leave such decisions up to the individual companies.

"We've been trying to read a very fine line between pure protectionists and pure free-traders, Brock said.

Reagan was a great listener during cabinet debates on the auto question, he added. "One thing I like about his style," Brock said, "is he wants to hear everybody out."

What is Brock's style? "Pretty much the same. That's why I like his," Brock laughed.

Brock, 50, was born in Chattanooga, Tenn., an heir of the Brock (not Brachs) Candy Co. He graduated from Washington and Lee University with a bachelor of science degree in commerce in 1953. Even then, he said, he was interested in international trade and economics.

He entered active U.S. Navy duty from Officer Candidates School as an ensign in 1953, served in Japan, Korea, China, Formosa, the Philippines and Indochina. He was released as a lieutenant J.G. in 1956.

Brock's affiliation with the Republicans started in 1960 when he quit the Democratic party and began working for the G.O.P. on county-level committees. He was also national committeeman from Tennessee to the Young Republican National Federation.

Brock won election to his first term in the House of Representatives in 1962 by a slim margin. Political analysts traced his victory to a bitter Democratic primary fight that split the party, in addition to defections of blacks to Brock. Even then Brock preached about "reaching truly free competitive world trade" and promised to combat "excessive federal spending" on the grounds that "if we spend more than our income . . . the day of reckoning must come."

Brock, who said he played the part of broker during cabinet-level discussions on the auto issue, is still cagey on what position he personally took.

His posture is reminiscent of billboards plastered around Tennessee during his successful Senate bid in 1970. "Bill Brock Believes," the billboards said. When attacked for running an issue-less campaign, the Brock campaign changed the billboards to read "Bill Brock Believes What We Believe."

When asked for his position on the auto issue, Brock said, "I have resisted saying anything on it . . . . I'm just reluctant to suggest to them any action."

Brock said he doesn't know how well Chrysler will fare during the remainder of his term in office, but he said, "there's a real prospect" the auto industry faces a period of shake-out." There will be more international companies and few companies overall, he said. "I hope our companies at least are good, healthy world exporters again."

Brock said the auto issue probably will be resolved before Prime Minister Zenko Suzuki visits Washington in May but that he doesn't know the end result. The Japanese could opt to restrain levels of imports for "a realistic period of time, and that's three years," increase purchases of American auto spare parts or invest in the United States, he said.

Brock said he hopes to use the auto issue as a steppingstone to opening up markets in Japan to U.S. firms.

As for his political future, Brock said he'll stay in his job as long as it remains challenging. Will he run for public office again? "I'm not sure I can contribute as much [in Congress] as in this capacity," Brock said. "In the last four years I learned how much fun it is to make decisions and make them stick."