You may have a bad main chassis power cable connection at your solenoid. If so, the problem is that after your engine first starts, the current flowing through the bad connection starts to heat up causing a high resistance condition. After a short while, the resistance becomes so great that very little current flow exist. Which means your ignition module no longer has the proper voltage and current to work correctly.
After giving the connection enough time to cool down, you can crank your engine again.
An easy way to see if this is the problem is by letting your engine run and then feel the cable insulation coming from your alternator towards your solenoid. If the cable becomes too hot to touch, then you have a bad joint connection where it ties into the chassis power cable and it needs to be re-terminated with a good solder joint.
This may not be the cause of your problem, but it was for my Jeep and it made a huge difference after it was fixed.
'77 CJ-5 Renegade 304 / T-150, Dana 20, 30/20 axles, Aussie Locker in the Dana 30, American Racing 15x10 Outlaw II's, 33" Dynapro M/T's" ,Optima Battery, TeamRushed + Summit Racing CDI ignition, FlowKooler water pump, Edelbrock Performer Intake Manifold, Holley 4160 390cfm, Herculiner, Silver Ceramic Coated Hedman Hedders, Flowmaster 40's.
Warn PowerPlant HD 12K Winch, Dirtworx front and rear bumpers.