In April of this year my radio dropped the codes. With advice I recceived in this NG I was able to correct that problem.
Now I've got a new one. Instead of flashing "codes" at me, it flashes "muted" and the radio goes off. It'll come on again later without me doing anything, then it'll go off again and give me the muted sign. I've done nothing to mute the radio. I wouldn't know how to mute it if I tried (other than turnining it off).
A couple of weeks after this problem began I noticed the red light by the rear view mirror (the M-B equivalent of GM's Onstar) was flashing. Since then I glance up to check everytime the radio goes off and sure enough, each time the light is blinking. And sometimes I briefly hear a phone sound like a dial tone. I carry a cell phone like almost everybody else but I have no built-in system that allows me to have a hands-free operation. I could understand the need to mute the radio under those circumstances but that does not apply. (The M-B Onstar hardware exists but I do not subscribe to the service)
Conicidentally --- this stuff began about the same time my decklid started popping open.