I had the privilege of finding and fixing this problem in a 2006 318. After some measuring i saw that the charging current on the battery was only 13,4 volts, thinking the alternator was bad i measured the voltage on the alternator. It turned out to be 14,2 volts. After examining the cable that runs from the alternator to the starter and to the battery it seem's to have suffered some overheating so i replaced it, and voilla all engine and electrical gremlins disappeared even the glow plug light behaves.

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600SEL '91
300E 4Matic '88
240D '83
280SE '77
350SE '73
The most complex systems can fail in the simplest way.
Contra verbosus noli contendere verbis, sermo datur cunctis, animi sapientia paucis.

i don't believe in the lord! He's never bought me a Mercedes Benz.