I disagree with everyone. I had the exact same symptoms and it turned out to be a bad caliper. I had to emergency brake and blew the caliper, once it was replaced the disappearing reappearing brakes never happened again.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42