[Tommy]

This can be hard to diagnose if it only happens occasionally, but here are my thoughts. If you are seeing a strong drain on the system when you engage the starter, but nothing else is happening, it is not likely the clutch safety switch. That would interrupt the signal from the ignition switch to the starter so there would be no drain. .... My guess is that the heat is causing an intenal short inside the starter. That would explain both the large current drain and the lack of starter movement. ... The only way I know to confirm this is to bypass all the external wiring and manually supply power to the starter with a jumper cable. This can be dangerous so use extreme caution (e.g., out of gear, wheels chocked, don't touch the wrong thing with the hot jumper cable). Plus it will only confirm the starter as the problem if it failed to work immediately before the test. If you let the car sit for a while before you jump it, you won't know if it cooled enough to "fix" itself.

If this were my car I'd first check to see if there was any way to shield the starter from exhaust heat (e.g, wrapping on starter, wrapping on exhaust, metal shield between the two). If it was already shielded or there was nothing that could be done, I'd get a new starter as was mentioned above.

Good luck sorting this out.