Losing power

I have a 94 Honda Accord with 153,000 miles on it. Twice in the last month it has lost power and the engine has quit while I was driving. The first time, it restarted after sitting for about 15-20 minutes. The 2nd time, it would not restart and was towed (on Sat. night). When the mechanic checked it out on Monday, it was working fine and he could not get it to “act up.” The tow truck driver thought it was the fuel pump. Others have suggested the distributor, alternator, or vapor lock. The first time, I had been driving it for about half an hour. The second time, I had been doing errands and had been driving about 20 minutes when it quit. In between those two times, I drove it for 1.25 hours (twice) without a problem. The mechanic said there’s nothing he can check when it’s running ok. Any suggestions? Or do I wait for it to quit again and hope it’s not bitter cold like it was Sat. night?

To narrow it down you really need to try and determine what’s missing when it quits and will not start.
Probably the easiest thing for a DIYer to do would be to carry an aerosol can of carburetor cleaner. When it quits try spraying a healthy shot of cleaner in the air intake. If it starts then you know the problem is lack of fuel.

Lack of spark could be distributor, ignition switch, etc.
Lack of fuel could be failing fuel pump, ignition switch, etc. or even a main relay. The latter is a common failure and you could replace that as part of a guinea pig test.
There are other things it could be but those mentioned are the most likely.