Truck intermittently won't start. Troubleshooting

I had this exact problem, ended up being the small found from the negative to the side of the engine wall was all corroded

 

Bingo!

Clean on the outside means nothing. If your cables are original to your truck, it's time for a change anyway. This is your problem, gauranteed.

 

Could be, they are original.

 

I would first check and see if the battery is fully charged and then load test it or substitute (or jump from) a known healthy and fully charged battery. If that does not fix the problem, then I would remove, clean, and tighten all of the power and ground terminals in the electrical path to your starter. There needs to be very low resistance connections to carry the high current (200 to 500 amps) to the starter motor. If there is a clicking sound when I was trying to start the engine, then the starter solenoid contacts are most likely burned and would need to be replaced. Intermittent problems are often very frustrating to find and easy to fix.