JB:

Shot in the dark here.

It seems you have an intermittent issue. I'm dealing with one as well, although I "think" I have it figured out.

You have changed a lot of items that can cause this, but I wonder if maybe a faulty ignition switch( the part that plugs in from the back) could be ailing you? I have not studied a schematic for this item and therefore wonder if it could supply elect. to turn the starter, but not necessarily the ign. circuit?

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"