My 2006 C280 has the driver's headrest stuck in the up position. Pressing the button on the door just gives a faint 'click.

 

Discovered the problem. The problem is in the little harness connection. Check yours out by removing the back of the seat and examining the little harness and connection up just beneath the headrest motor. See if it is too loose to stay together by itself. Use ties or whatever you can work with to draw this connection tight and fasten the little plug to the little board

 

You should probably check your fuses first, but with the 'stuck' problem none of mine were blown. The panel on back of the seat might be difficult to remove. Unfasten two bolts down at the bottom of the panel. Maybe you can slide the panel down far enough to work on the wiring connection. In my case the seat panel broke off of its holding brackets, but I will get the panel back on by using other type fasteners. I think it is worth it to get the headrest working. It needs to get back to adjusting because its position is important to safety.

 

Tried tying the little harness to the little board with strong thread, and then again with fishing line. This proved too difficult because of the small space and the plug kept falling away from the board. I then used a little crazy glue (didn't have gel, so used all-purpose). I dabbed a little bit of glue on the black 'prongs' that went into the board. You need a small stick about the size of a toothpick, only something longer, to smear on the glue. Be careful not to let the glue get on where the electrical prongs have to make the connection. While squeezing the harness into the board, your fingers could get glue on them, so be ready to rinse them off with water. I don't know how plastic gloves would work, but I didn't want to get anything like that stuck to the connection. The glue was left on the connection overnight and served the good purpose of holding the plug tight enough to add a piece of small gauge wire threaded behind the board, between the black pins and around and up between the two center wires on the plug. This wire was insulated with no bare spots or bare ends. It was a single strand instead of fine multi-strands (single strand twists into a 'tie' better than multi-strand). A few twists with a needle nosed pliers helps, but don't overdo it and break something. Done correctly, this will be a strong connection and done safely.