1993 Honda Accord Sporadic Engine Failure

I have an early '90s Honda Accord that runs great almost all the time. Once every few months, it inadvertently dies. It's happened on the freeway, on normal city streets, and sitting in the parking lot. The car will begin running rough, and the tachometer jumps around from zero up to 4 or 5 thousand before finally conking out. It has happened at least 10 times, and each time I pull over, put the car in park, turn the key to the off position and wait a few minutes. Sometimes the car will crank but not come on, so I wait some more. It has never taken more than 10 minutes to come on again, and then it will work like a dream for another 1 - 3 months.

I took the car to a mechanic who told me they could run diagnostics but it likely wouldn't happen at the right time, and I'd just be out a $100. (Went a long way to earning my trust!). I'd like to take the vehicle on a road trip for the holidays, but I'm concerned about it's reliability. What can I do to get this taken care of?