'89 Trooper stalls

My small engine '89 Trooper with 157k is used for errands around town. It was tuned a few months ago and runs beautifully. Starts right up every time. BUT two times this month it stopped running while waiting at a stop light, and refused to re-start for nearly an hour. This is all-or-nothing. It's either running perfectly or not at all, then fixes itself. When it won't start it either doesn't fire at all or doesn't get fuel. [I haven't yet been able to check which.] What parts, sensors, etc. Are likely to become suddenly inopperative and a few minutes later suddenly operative again?