I have a 1972 spider and am the third owner for the last 6 years. Every year I have encountered the problem below and have been to many mechanics but no one has yet to figure it out

Heres the issue - sometimes after driving my car when I turn it off and go to turn on the car again it wont start again. Its not a battery issue - all the lights will go on - and you dont hear any sound when you turn the key. The wiring seems to have been checked and the starter has been replaced. The strangest thing is that after waiting time - somethimes a few hours or in this last episode a few days the car will start again no problem.
Has anyone else encountered this problem or suggest what to look for - Im going to check thr ground wire again. Much appreciated!