How do you know the switch is good - you tried it in another car or you checked continuity? If you checked continuity then you know the pin-outs. Jump the corresponding pins in the socket and see if that does it. If you tried it in another car, try the other car's switch in this car (I'm grasping now). Give the switch a good spritz of Caig Deoxit to clean it.

If nothing works, raise the seat as much as it will go. You'll see a bunch of motors under the seat. It's easy to identify which motor does what by having someone tap the switches while you feel for which one's vibrating. Make sure your second pair of hands knows to only tap the switches because there's a lot of finger crushing torque at the end of those reduction gears.

Pull the bum motor and see if it's a bum because it's dead or because the mechanism's stuck. If it's dead, bury it. If the mechanism's stuck, see if you can free it. It gets even more generic at this point because I don't know if the reclining mechanism has a straight gear drive or a cable drive and if it's possible for the mechanism to jump its rack at the extremes of travel. So many possibilities but it's pretty obvious how the mechanisms work once you see it.

Probably just a dirty switch or bad connector

Hope this helps.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD