Try wiggling the key just a touch. I noticed this same thing on the 560, no blower on occassion. Found that every once and a while the key would not fully return to the run position. Slightly moving the key broght the blower back to life.
Also, seat adjustment didn't work when the key was off it's mark.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.