did you convert to european headlights? if so, that is why.
The conversion didn't cause any problems on my 300E with stock '+50' Philips 55watt H4 bulbs. What would be the source of the problem, (except maybe using an overwattage bulb as the STAR article discusses)?
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E