Asked at a recent Washington cocktail party whether he, like former White House chief of staff James Baker, feels "burned out" by the rigors of his job over the past four years, 62- year-old Commerce Secretary Malcolm Baldrige didn't hesitate.

"Hell, no!" he exclaimed: "I'm just getting warmed up."

In a relaxed interview in his paneled Commerce Department office, Baldrige said that the corporate boardroom no longer holds "that much interest" after 28 years as the chief executive officer of two companies, "whereas this job is fascinating."

Thus, so long as President Reagan wants him to stay in the Cabinet, he's gung-ho: "You're constantly learning. Sure, you lose plenty on issues that you may not be able to get through on completely, but then you win some too."

But it looks as if Baldrige is about to lose a big one -- his proposal to fold Bill Brock's Office of Special Trade Representative into Commerce, remaking it into the Department of Trade and Industry.

Critics, including Secretary of State George Shultz, have argued that Baldrige wants to create a centralized trade policy power center similar to the Japanese Ministry of International Trade and Industry, a "DITI" to cope with MITI.

A presidential decision is still to be made, and Baldrige bravely said that the fight is not yet lost. But favorable mention of a DITI was conspicuously absent from the State of the Union message.

Nonetheless, Baldrige has been one of the more successful commerce secretaries of the postwar era, earning the admiration of the White House as a solid team player and of the Washington press corps for his accessibility and candor.

The unfocused, unwieldy Commerce Department bureaucracy has troubled many a Baldrige predecessor. A frustrated Juanta Kreps left the Jimmy Carter Cabinet after she discovered how limited Commerce's influence was in setting macroeconomic policy, even though it grinds out most of the statistics that other advisers use as a basis for their own advice to the president.

Baldrige hasn't tried to make macroeconomic policy. But he has carved out an increasingly important role for himself by concentrating on trade issues, generally assuming a hawkish position on the ever-present and growing problem of the bilateral trade deficit with Japan.

"We aren't going to change our position away from free-trade principles," Baldrige told me. But he argues that if Japan positively encouraged imports, in accord with commitments Japanese Prime Minister Yasuhiro Nakasone made to Reagan a few weeks ago in California, the $35 billion Japanese surplus with the United States could be cut by "at least $12 billion."

He acknowledges that for Nakasone and his Cabinet to leadtheir country "into accepting responsibilities for being the second-largest industrial power in the world is a difficult job for them. We all recognize that. You won't get the bureaucracy or the industry in Japan to want to change their ways.

"People understand comparative advantage (in producing and marketing goods). What they can't understand is other countries' closed markets in the face of our open markets. Considering the volume of trade between us, we don't have any restrictions to speak of, except the voluntary restraints on cars, and there'll be a decision soon whether to keep that or not."

That decision has now been made: the Reagan administration won't ask Japan to restrain car exports after March 31, despite complaints from the Ford and Chrysler companies that they still need protection.

"There isn't a lot of sentiment in the administration for (retaining quotas)," Baldrige told me. Of course, if the Japanese themselves want to limit car exports -- as they probably will -- that will be up to them. (It would be the first time in five years that such restraints were truly "voluntary.")

Baldrige admits that his fight for a DITI had become a battle over "turf": Brock and his STR office would be the most seriously affected, although Baldrige thinks Brock's objections were softened by the secretary's willingness to see a coordinating council in the White House to consider trade and overall economic policy together.

But working against Baldrige is the more general view in the administration that a DITI would dampen the STR's open-trade instincts, while becoming a haven for anti-competitive forces.

"It's gotten to be somewhat an emotional subject," Baldrige said. "There's clearly some turf involved, and I don't think that decisions ought to be made on the basis of turf, but you can't go against human nature."

Baldrige is so convinced of the need for a Trade Department that he keeps on hop"I just don't know how it's going to come out," he says. But one thing is certain, even if he has lost on DITI: so long as Reagan wants him, Baldrige will stay on at Commerce: "I make no bones about it; I really like being in the government."