There is a combination wiper RELAY (not a fuse) on the engine compartment that it is usually the culprit for this behavior.
Find out the part number at PartsShop, order it and replace it, and your problem should go away. It did for my E 320 T which had the same exact problem.
CL 500, 1998
S 500 L, 1998
E 320 T, 1995