Radio cuts out intermittently except when key off
 

I have a '99 Carrera with a radio that cuts out, display and all, for about 15 minutes after the car is started. Then it will stay on fine and be OK if the car is off for a short period. The radio will, however, work just fine with the key off but not removed. The battery is new, the ignition switch is new, the fuse is good and cleaned. Any suggestions?

Ground maybe wonky.....

+1 for the ground wire being a pain. I've attached a link below that shows the various wires and connectors/pins. Hope this helps and best of luck!

Porsche 911 Carrera Radio Head Unit Installation - 996 (1998-2005) - 997 (2005-2012) - Pelican Parts Technical Article

Further investigation of my radio issue revealed that the radio actually works in both the off position and the on position, as long as the engine isn't running... I am looking at the ground situation and trying to see if there is anything odd about the power when the alternator is running. The voltage remains stable when charging and the radio functions fine after about 5-10 minutes and mostly for the remainder of the day,