I think you need a new seat position combination switch located behind the door handle.
You can also try to take the switch apart and to lubricate the parts as well. ( Be careful of those little ball bearings )
Peter Chu aka PIKACHU
08 C300 Premium Pkg, MM Pkg, Sport Pkg, Keyless Go
86 300E soon to be E36 with Euro Headlights
400E front & rear brake upgrade
16" CLK wheels with Michelin MXV4 plus Green X