It sounds like an electrical problem with your ABS. The sensors at the front wheels maybe dirty. Sometimes cleaning the sensors can help. It could be a bad connection in the ABS wiring somewhere, or could be the ABS sensors starting to fail. There are numerous posts on this subject. If you get a chance, scan the archives.
Good luck.

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1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T