2000 S430 audio system
 

What is the problem when the audio for the command system (navigation and radio) will sporadically go off and on. However, if I pull over and turn the car off, wait about 20 seconds and turn the car back on again , the sound will come back. Does anyone know what might be the cause for this?

There are lots of issues with this thing. The dealer can actually do software updates which fixes lots of things such as this. I believe they would be free updates too, may even have a service bulletin for your specific problems.
It could also be a bad COMAND unit or other component in the sound system or a misconfigured fiber optic system.

Gilly