Lyn Nofziger, President Reagan's former political adviser, was depicted by prosecutors as an influential lobbyist out to make a buck and by defense lawyers as a gruff ex-newspaperman eager only to make enough "so he and his wife could be comfortable" in opening arguments yesterday in his trial on conflict-of-interest charges.

Nofziger repeatedly tried to cash in on his White House connections soon after leaving the White House in 1982, Lovida H. Coleman Jr., the deputy independent counsel, told a jury in federal court here.

"Mr. Nofziger's life had been power politics and influence, but he never before cashed in on that influence," Coleman said. But once he and his partner Mark Bragg went into business together, the jurors were told, Nofziger kept contacting "friends and colleagues at the White House in a manner forbidden by law."

As Nofziger sat at the defense table with a fresh Mickey Mouse tie, his lawyers countered by assailing the government's case as a half-baked concoction of exaggerated facts and confusing law.

Nofziger's attorney, E. Lawrence Barcella, said that nothing Nofziger did violated the untested section of the Ethics in Government Act under which Nofziger is being tried.

"The law does not drop a curtain between a former official and his agency . . . and say, 'That's it,' " Barcella said. He added that the statute imposes a one-year ban only on lobbying one's old agency about matters that are of "direct and substantial interest" to that agency.

He maintained that the causes Nofziger promoted at the White House among old friends such as then-White House counselor Edwin Meese III and Meese deputy James Jenkins were minor-league issues that did not fall under the proscription.

As for cashing in, Barcella said, Nofziger was 57 when he left the White House and after a lifetime as a newsman and political aide "he didn't have a retirement fund."

The opening statements began what is expected to be a four- to six-week trial before U.S. District Court Judge Thomas H. Flannery.

Nofziger, now 63, has been accused in four felony counts of illegal lobbying, twice on behalf of the scandal-ridden Wedtech Corp., and twice for other clients, Fairchild Industries and the Marine Engineers Beneficial Association (MEBA), a labor union.

Bragg, 42, was indicted for aiding and abetting in one episode involving Wedtech. Bragg's lawyer, Richard Ben-Veniste, maintained that his client went to bat for Wedtech, thinking it was a good cause and not "a one-company crime wave" of bribery and payoffs. All that came out much later, Ben-Veniste said.

The first witnesses yesterday afternoon told of Nofziger's lobbying of the White House for MEBA on Aug. 20, 1982, the day after the labor union had given the administration a helping hand in steering a controversial tax increase through the House of Representatives.

Rose Marie Monk, Nofziger's former administrative assistant, said President Reagan had persuaded Nofziger to come back to the White House and drum up support for the bill. The day after the vote, she said she typed a number of thank-you notes for Nofziger, including one to MEBA president Jesse Calhoon.

Nofziger, the jurors were told, sent carbons of the note to Jenkins, Meese and then-White House chief of staff James A. Baker III with a postscript pointing out that Calhoon had been trying to "to get action on civilian manning of some naval ships, without result, even though the president has asked that it be done."

Calhoon, Nofziger added, has "been supportive of all the president's endeavors, including the last one. Why not help our friends?"

Jenkins sent a copy back to Nofziger again with another note in Jenkins' handwriting that said: "Lyn -- Cap {Weinberger} assured the Cabinet council meeting on maritime policy that this is being done!"

David Keene, another MEBA lobbyist, testified that Vice President Bush had given him the same report about Weinberger, but Keene said nothing came of it.

At the White House, Keene said MEBA's campaign to get civilian crews on Navy ships was given lip service, but "no one ever did anything about it."

Nofziger's lawyers suggested this fell far short of "direct and substantial interest."