Strange issue once in a while.

I guess the first place I would look is a white harness connector under the steering column. Makes ignition switch to car harness. These connectors overheat to melting.
Then again... my bro-in-law had similar problem with his c10 pickup. The wire to neutral safety switch was hacked and pieced with wire nuts. 3 pieces of wire. Easy enough to test that. Route that relay terminal directly to ground for a time. Beware that starter would activate while trans is in gear.