Striking physicians and representatives of the Group Health Association resumed negotiations yesterday with the help of a federal mediator to try to resolve differences and end the walkout that began Saturday morning.

Negotiations recessed yesterday afternoon after more than five hours of talks and were scheduled to resume this morning. A member of the physicians' negotiating team said yesterday that "much of the heat, much of the discord . . . has dissipated" and that negotiations "are moving again."

The 55 physicians, responsible for the care of GHA's 109,000 members, voted to strike Friday night after rejecting the health plan's final contract offer.

Despite the strike, members of the physicians' union said they would continue to treat their patients who are in the hospital and take their regular turns answering emergency calls.

A spokesman for GHA said yesterday that 28 physicians, including four surgeons, were working, another four were on call and four part-time physicians had worked. In addition, another 24 physician's assistants, able to handle routine medical problems, reported for work.

Routine appointments were cancelled for yesterday and today. Emergency problems were being handled at GHA's main location at 2121 Pennysylvania Ave. NW. The health plan's medical clinics in Virginia and Maryland were closed, but dental clinics and optical and psychiatric services continued to operate normally, according to the spokesman.

Striking physicians have said that economics are not an issue in the strike. GHA offered, and the physicians have accepted, a salary package that calls for average annual pay to go from $53,000 to $60,000 immediately, and to $66,000 in 1979.

The issues dividing the physicians and the health plan officials, who have been negotiating since January, involve malpractice insurance, continuation of a ban on outside practice by physicians and the number of clinic hours that primary care physicians must observe.

The strike inconvenienced some patients. Kent Smith, an economist who works at the Justice Department, said yesterday that he had trouble getting GHA to look at his 23-month-old daughter, Kimberly Ann, who had been running a fever for 24 hours.

Smith said he called his GHA physician and was told to call the emergency number. When he called that number, Smith said, he was told his daughter was not sick enough to be brought in for examination.

Smith said in a telephone interview that "the association is doing all it can, although it wasn't much help telling us how to arrange for a doctor."