1993 Chevy Silverado starting

It wont even turn over now.

Did you meant it cranks over and will not start or just won't crank at all/nothing/nada?

Cranks and w/n start

Get a helper disconnect a sparkplug wire or 2 and ground it to the engine -have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs, coil's resistances, distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it

No crank at all/nothing/nada:

Could be the starter, starter relay, park and neutral switch and ignition switch assuming the battery and connections are good.

Sounds like a crankshaft position sensor to me. (The accumulated heat from your engine is affecting the sensor signal). At least, that is the first thing I would check.