[Joe Bob]

Typical for BOTH the 914 and 911. Heat expands the starter solenoid. The grease inside gets old and and the heat gives it the excuse to not work. A whack on the solenoid "usually" frees it up.

The solution is to find a new old stock unit and replace it.....or just be aware of it or whack it when it happens or learn to pop the clutch......

Lots of people go with the more modern Japanese starters since the Bosch units are NLA. Not a fan. My rebuilder still has access to good quality parts. YMMV

BTW if you see a NEW Bosch starter for your ride and it's new old stock....grab it. All other are remans and ain't worth spit in most cases......yes they have a warranty for life but YOU eat the labor.

EDIT....another solution is the Ford starter relay, "Hot Start" kit. Seems to work......have to look around for it. Try Glenn Sager at Pelican, he is familiar with it