Does your model have coil packs? My 1997 C280 (I6) has a coil pack for each two cylinders and I have had to replace two already, the second just last week. (87,000mi.) When mine went out there was occasional backfiring and sluggish acceleration along with the check engine light going on. Simple to replace and with discounts cost approx. $90.00 each at the dealer.

Tim