Uh oh. I had a similar behavior in a Mercedes several years ago. Scary as hell to get pressed against the steering wheel, and intermittent so it was difficult to diagnose. In my case, the shop could not find any problem after taking out the switches, seat controller, wiring harness, etc., so they reassembled it and the problem seemed to go away. We also tried replacing the controller but it did not seem to make a difference. So I concluded that the components were ok but that there was a loose connection someplace (most likely a ground) and that the dealer's reassembly corrected it. The car was a heck of a lot older than any of the cars mentioned in this thread, but there still might be a loose connection or poorly installed ground somewhere.