I have a 2000 k2500 7.4 l w @ 72000 miles. It started that very occasionally when stopping to get gas or a coffee, I would come out and have a no start. A quick test would show pressure but unsure of how much as didn't have gage with me. After 5 secs to 10 minutes it will restart, usually just seconds though. I started carrying a scanner and 1 time the scanner said unable to obtain data not unable to communicate, leading to believe pcm issue. Removed pcm and disassembled and found one melted circuit inside, so replaced pcm. prior to this as purely educated guess, replaced crank sensor, coil and module with no improvement. It never last long enough to do a proper diagnoisis.
Now when driving it will feel like ignition turned off and then will come back as pulling off road. prior to pcm replacement it did die at highway speed. Today it started to die and be unresponsive 3 times while driving but never stalled and continued to drive ok after a couple seconds. My gut is saying ignition switch but an looking for others input in a issue similar.

 

It's hard to say unless you can get a proper diagnosis of the problem while it's happening ... I've seen some strange things happen from a bad fuse block. Perhaps a grounding issue with the PCM? As far as I'm concerned, putting a new ignition switch on it wouldn't hurt all that much. At least you'll know your ignition switch isn't the problem lol :P