Try pulling the fuse for the seat heaters and see if that does anything.
The intermittant ABS light while driving is a classic MB symptom of a failing alternator, and many people have spent many hours pouring over their ABS system to find that it was a charging system fault. Me included.
You might have more than one problem, but it's best to rule out the things that you can right away. You might have the charging system load tested, and then you'll also have a good idea of battery health.
1998 C230 "Black Betty"