I can drive for a few days and then it won't start. There is never any pattern to why it won't start. I have had the battery checked and the alternator checked and they are fine.

SOURCE: 93 won t start, clicking when i try to start... it

I would change all three. alittle expensive, but on this old of a vehicle I would not waste time and trouble. if this doesnt work then maybe some ignition problems. But i would guess that battery, starter, alternator, should do the trick

SOURCE: 97' nissan pick-up started dying while driving air

This is just a suggestion that may fit the symptoms. It sounds like you are not getting fuel at times which could mean that your fuel pump is supplying fuel, but your in line fuel filter is getting clogged and not letting fuel pass to the injectors. The fuel that has mandated alcohol in it is highly hydroscopic and picks up a lot of water that ends up in your tank and mixes with the rust that it causes on the steel tank. That gunk is sucked up by the pump and under pressure blocks your fuel filter after a while, and is so impacted that it cuts off the fuel flow stalling the engine. If you let it sit for a while, then the impacted debris settles down in the bottom half of the filter allowing the fuel to flow, but under pressure it builds up at the exit port again. It could be as simple as changing the fuel filter.