SOLVED IT:
My '94, VG30E would only start intermittently when the motor was hot. Also, it didn't want to start if the outside daytime temperature was hot (with a hot or cold motor). I checked the fender-mounted relay first (had caused this problem once before) and fuses, then checked that the motor-to-chassis ground straps existed. When I cleaned the battery cables (both ends of both), one of the nuts on the starter "stripped" (bolt was loose inside the starter and just spun) so I replaced the starter with a new Bosch one. The problem still existed so I had the OEM starter bench tested. It showed a bad solenoid. So then I removed the neutral safety switch and it tested OK. I got in the steering column and found that the ignition switch was bad. Easy and cheap replacement. Problem solved.
So to summarize, when the motor was hot the solenoid would act up. When the air temperature in the cabin was really hot, the ignition switch would act up. TWO problems at one time. I sure hope this helps someone!
