My 88 560 sl did the same. Your post of 1/29 about intermittent no start fits the ignition switch problem too. Failure of other electrical components such as radio and blower when engine dies would be a positive indication of master electrical failure verses an obscure ignition part.
The switch can be had for about $40 on-line. DIY replacement (on the 560-sl) was < 1 hour. After replacement, it was apparent that the old switch could easily have been restored with contact cleaner and emory cloth.