98 jimmy dies after warm up

[98jimmy]

I have a 98 jimmy 4.3 liter 106,000 miles. The problem started 3 years ago when moving from Alaska to nevada and only occurs in summer. In hot weather only, driving 80 or 25 in town or idling, the engine will intermittently die after it gets hot. No problem with restart--I am use to popping it into nuetral at 75 mph and restarting on the fly. The problem seems to kill the engine but allows it to be restated with no problem. The engine is smooth as pie before/after this happens, no sputtering, just dead. mileage is normal. No error codes, no other symptoms--headlights keep shining, music keeps playing during these events. This might happen 3-4 times in a row ,once in a while or not at all when the GM mech is driving it. This is only a maybe but it seems like just pulling over , turn the ignition off/on maybe helps a little. I tried new ignition switch and fuel filter. local GM folks got nothin' I don't mind shotgunning the problem if I had a likely list of culprits. Help!