NEW YORK (AP) _ The National Association of Securities Dealers Automated Quotation system's computer was down for about 14 minutes at the start of trading Monday, inhibiting market makers from executing trades.

NASDAQ provides brokers and dealers with price quotations for over-the- counte r issues as well as many securities listed on the New York Stock Exchange.

Anthony Morea, NASDAQ's vice president of operations, said he did not know what triggered the problem, which began at 9:40 a.m. at the system's main computer in Trumbull, Conn., or whether a backup computer in Rockville, Md., was put into operation.

Morea noted that the computer failure occurred just after the market opened at 9:30 a.m., when trading typically is heavy. The system was down for about 9.5 minutes, and NASDAQ delayed the resumption of trading for about another five minutes to give market makers ''a fair shot at coming out of the gates,'' he said.

He said the computer failure was a rare occurrence.