Alright, Now we need to figure out what it's lacking when it won't start, either fuel pressure, injector pulse, or spark.
1. Scan for any codes, if you don't have a scanner, stop at a local auto parts store and they will scan it. If any codes are present that can point you in the right direction and give you something to go on as far as fault tracing goes, if there are NO codes stored, then follow these steps.
1. Just turn the key ON, when it doesn't start, See if the check engine
light comes on or not, It should come on when you turn the key to the ON position indicating the PCM is powering up. If it doesn't, I would first replace the PCM relay.
2. If you have a fuel pressure gauge or can get or borrow one, put it in the truck. Next time it acts up, connect the fuel pressure gauge to the fuel schrader valve on the fuel rail. We want to see if it has fuel pressure when this problem occurs. If it doesn't, I would replace the Fuel Pump Relay, and then if it acted up again, It's likely it could be a failing fuel pump in the tank.
3. If you have fuel pressure, check for spark out of the coil pack with a spark tester when it won't crank, if it does not have fire to the plugs when this problem occurs, I would first try another crank sensor. I beleive you'll find your problem in those steps.