1992 240 wgn automatic

starts fine when cold...however after it gets hot (30 minutes or more of highway driving), if i stop and wait more than 15 minutes or so, it wont start. i get no power to the starter. turn the key and nothing. radio and everything else work fine. eventually (20 minutes after it first failed to start), it will start up again.

more interesting data...if after the same 30 minutes of highway driving, i stop it and start it right back up (less than 15 minutes), it will start fine.

in the summer it is much, much worse. i am thinking perhaps it is a problem in the ignition switch/wiring, as when it happens, i get no power to the starter. perhaps the heat is causing a connection issue or something in the ignition switch?

my gut tells me there is some sort of wiring problem in the starting circuit that is made much worse by the heat. however i am open to any suggestions!!!

any help would be greatly appreciated!

thanks.