In the link I posted, there is a message about near the bottom discussing cleaning the starter replay terminals/connections. On spjohns1's, apparently just the slightest bit of discoloration/corrosion was enough to interrupt the flow of energy to the starter. Cleaning those connections seems to have cured the problem.
'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.