My 4matic did the same. For just over $74,000 new, it would turn off the heated seats and heated rear window if idling in traffic just after starting, ... the quattro would run the bun-warmers and heat the rear window fine at idle.

I don't have many complaints about how the 124s are built and how they hold up, even now that they're becoming senior citizens, but that one bugged me from the start.