Three months into his second term, President Reagan and his aides appear to have misplaced the magic public relations touch that has been a conspicuous feature of his presidency.

In the last 10 days, Reagan has been embarrassed by his decision to visit Bitburg military cemetery where Nazi SS soldiers are buried and buffeted by the prospect of congressional rejection of his plan to provide $14 million to rebels opposing the leftist Nicaraguan government.

Administration officials and prominent congressional Republicans say that the new White House team headed by chief of staff Donald T. Regan has stumbled in its attempts at damage control. One senior official, reflecting a widespread view, said Regan's predecessor, James A. Baker III, who now is secretary of the treasury, would have "undone the Bitburg blunder" within 24 hours of its announcement.

The setbacks for Reagan, on public relations and policy, occur as his administration's stability and his popularity may be undermined by surprisingly sluggish first-quarter economic growth. Chief of staff Regan responded to this news Thursday by acknowledging "at this moment, the economy is not healthy."

During the past week Reagan's luck also has deserted him on relatively minor matters that have added to the impression of floundering. Last Monday he honored a young "Nicaraguan refugee" who turned out to be the daughter of Nicaraguan Americans who have lived in the United States for 15 years. On Wednesday, at a state dinner, he uncharacteristically walked on the stage in the middle of a ballet, thinking it had ended.

Reagan's aides tend to see these problems, large and small, as temporary reverses that will mean little to the successful course of the Reagan presidency. Some in the White House maintain that Reagan will emerge a winner, or at least won't wind up a loser, on the touchy issue of securing aid for the Nicaraguan "contra" rebels.

Last week Reagan began his campaign for aiding the rebels with an emotional speech that followed the recommendation of communications director Patrick J. Buchanan, who wanted the president to follow up with a nationally televised speech this Sunday. By week's end Buchanan's confrontational approach had been supplanted by efforts initiated by national security affairs adviser Robert C. McFarlane to salvage a legislative compromise in the face of almost certain defeat in the House.

Reagan will talk about Nicaragua in his weekly radio speech today, but his televised speech has been pushed off to midweek and will focus on the budget, as Republican congressional leaders have requested.

"In January everybody in this town was saying that aid to the contras was dead," one White House official said yesterday. "If we can come out of this by keeping the 'humanitarian' aid alive, we will have done more than anyone expected and sent a useful signal to Central America."

But few officials are equally optimistic about the prospects for Reagan's budget. And they widely agree that Reagan has been severely damaged by his insistence on visiting a German cemetery where Nazi SS troops are buried despite the protests of Holocaust survivors and U.S. veterans groups.

Some of the criticism has been directed at Reagan, who dug in his heels rather than accommodating the protesters. Some have pointed at departing deputy chief of staff Michael K. Deaver for ignoring early warnings that Reagan shouldn't visit the military cemetery. And some officials say that both chief of staff Regan and Buchanan lack the political touch that distinguished their predecessors.

Regan's detractors say he has demonstrated political naivete in dealing both with the Bitburg cemetery visit and with the budget, which includes prospective cuts in the cost-of-living allowances for Social Security recipients.

A White House axiom in the first Reagan term was that no cuts should ever be proposed in Social Security unless Democratic leaders agreed in advance to support them. Reagan's aides learned this the hard way after Democrats made a midterm campaign issue of Social Security cutbacks proposed by Office of Management and Budget Director David A. Stockman in 1981.

When the White House engineered a Social Security compromise in 1983, Baker and his principal deputy, Richard G. Darman, insisted that Democrats commit themselves to the package before Reagan did.

This time Regan committed the president and proudly took credit for a budget package that included Social Security cost-of-living increase cuts. Democrats gleefully have quoted from a post-election interview of Reagan with Human Events in which he promised not to make any such reductions.

The Bitburg visit was scheduled before Regan became chief of staff. President Reagan agreed to it in November in the mistaken belief he would be going to a cemetery where both U.S. and German soldiers were buried. Deaver subsequently visited the cemetery and approved the stop on Reagan's itinerary. National security adviser McFarlane and State Department officials later signed off on the plan.

Privately, U.S. officials say that the West Germans were "not keen" on a concentration camp stop, fearing that the left-wing Green Party would turn a commemorative ceremony on victims of the Holocaust into a demonstration against U.S. missiles in West Germany.

But after the West Germans recognized that a concentration camp visit was a political necessity for Reagan and formally invited him to visit Dachau, no one seems to have reviewed the matter with the president. Offering an explanation Thursday of what had happened, Reagan said, "I thought that the suggestion had come from an individual and was not a part of the state visit."

When White House spokesman Larry Speakes announced the Bitburg visit on April 11, Regan decided to wait and see how it played on the networks. Both he and Speakes initially took comfort from that night's network news, officials said, because only CBS played it as a major story.

But the story made most front pages the next morning, and it built day by day without any effective response from Regan or other staff members. Buchanan reportedly told Reagan not to change his plans because this would be "caving in" to the protesters, words Reagan used Thursday. Buchanan reportedly was also the source of the language Reagan used in saying the German soldiers buried in the cemetery were "victims of Nazism" like the victims in the concentration camps.

"This could have been turned around a week ago," one official said. "Reagan had the perfect out because he could honestly say he didn't know that SS men were buried in the cemetery he was to visit. But he is a passive president who waits for others to draw the options. This time no one did."

By yesterday, on what White House officials referred to as "Day 9 of Bitburg," the president was thoroughly committed to the visit. All lines of retreat appeared to have been cut off.

In conversations with his aides yesterday, Reagan did what other presidents have done in similar moments of difficulty: he blamed the press.

"The president is frustrated," said a senior official late yesterday. "He feels like every time he's explained why he's doing what he's doing, it has been turned against him. Frankly, he blames the press corps for spreading this story.