Will try to sum it up: Most of the time, the thing starts like a charm, first try. Every now and then, though, I’ll turn the key and either a) nothing will happen or b) it will slowly crank and eventually start. If nothing happens, I have always been able to try again seconds later and everything works OK. Have been through several batteries. Current battery checks out OK, as does starter and alternator.
A short circuit, perhaps? If so, how would I check it out?
Problem with taking it to a mechanic is, most of the time all is OK. No pattern as to when the trouble will occur (has yet to happen with vehicle in the shop, of course).