One problem related to fog lights has been reported for the 1998 Mercedes Benz 320. The most recently reported issues are listed below.
Car started burning out light bulbs and horns, 25 incidents, from 02/15/1998 to 03/06/2002. Two dealers were unable to fix the problem. Lights included tail lights/ headlights/ fog lights/ side markers. I have seen other mb e320's in the dealers for same reason.