00 Jeep Grand Cherokee, turns off while driving or parked. It will crank but, no start.Turns back on in a few minutes, but lately it has been longer and longer before it turns back on. I notice it happens after the engine as warmed up.

SOURCE: engine will not fire or run,but turns over like it should.

Not sure if it will be the same for your model of Jeep but but I had the same problem with my 98 Cherokee. Turned out to be the Crankshaft Position Sensor. Sits on the upper drivers side of the tranny and can block voltage to the fule pump and distributor. Found it by getting a error code reader from AutoZone (free loan) and looking up the error code. Replaced the CPS ($89) and started right up.

SOURCE: 2002 Jeep Grand Cherokee Lardo misfiring

You say you changed the cam sensor. A1391 code is a crank sensor on the top of the trans. bell housing.

SOURCE: 2001 Jeep Grand Cherokee 4.7L crank no start

easy trouble shoot easy fix ! check to see if its getting fire if not replace the crank sensor it will fire right up common problem with the jeeps . Hope this helps you out !!!

SOURCE: 1996 jeep grand Cherokee 4.0L no power at coil got

TRY THE PLUGS ,CAP&ROTOR CHANGE THE FUEL FILTER,STILL NO START,THEN CHECK THE FUEL FILTER NOW, IT SHOULD BE WET,IF NOT THEN YOUR FUEL PUMP IS NOT WORKING

SOURCE: Jeep Grand Cherokee Power Loss

a bad cam sensor will cause vehicle to shut off while driving, and cause a hard time starting. but this usually sets a trouble code p0340. scan vehicle to see if any codes come up. after it is fixed, erase codes with a obd2 scanner. if you do not have one, you can go to any auto parts store and they will erase codes for free.