The nation's major retailers yesterday reported mixed sales results for May, with some chains ringing up disappointing figures that contrasted sharply with April's brisk overall performance.

"It's kind of a mixed bag," said Linda Kristiansen, a retailing analyst for the investment firm PaineWebber Inc. "I think most of {the sales results} were on the soft side. It was one of the weaker months so far this year."

Sales in May were dampened by a sharp decline in Americans' disposable income and by consumers' widespread efforts to pay off some debt, analysts noted.

"We believe consumer spending remains restrained by continued high installment debt levels, as well as the adverse effect of some increases in inflation on consumer attitudes," said Jeffrey Feiner, who follows the industry for Merrill Lynch & Co.

"Basically, {the May sales} look soft," concluded Jeffrey Edelman, an analyst for Drexel Burnham Lambert Inc. "It points out that the economy is not running away, that we still see weakness in the economy."

The May sales results "reconfirm the fact that the economy is in a very slow growth period and consumers still are cautious," Edelman added.

"Several retailers, including J.C. Penney and F.W. Woolworth, noted that their May results were above expectations and benefited from strong apparel sales," said Feiner. "Others, including Sears, Roebuck, were adversely affected by a continued weak durable goods climate."

Industry leader Sears saw its May sales increase only 2.2 percent from the May 1986 level, to $2.262 billion. The weakness was largely due to the retailer's mix of merchandise, Sears spokesman Ernest L. Arms said. About 65 percent of Sears' wares are "hard goods" like appliances and furniture, which generally were slower sellers in May than apparel and other items.

"We were very strong in apparel," Arms said, citing record sales in women's apparel during the month. He also noted strong gains in sales of refrigerators, freezers, telephones and air conditioners.

Other retailers that carry a larger proportion of apparel were able to benefit more strongly, as apparel sales were boosted by unseasonably warm weather in some parts of the country, analysts said. "Apparel was where the relative strength was," said PaineWebber's Kristiansen.

"The unwillingness of consumers to go further into debt has had a much greater impact on big-ticket durable goods than apparel sales," said Monroe Greenstein, analyst at Bear, Stearns & Co. in New York. Consumer electronic sales have slowed dramatically this year, he said.