Originally Posted by Gregory891

It's a good question, however E53 don't have automatic seat heating. It's activated by the switch strip just in front of your front ashtray. Switches are at the extreme left and extreme right.

Italian market E53, I have one originally with cloth mechanical seats. I retrofit heated leather sport seats up front, leather rear (no heat) and the matching door cards. Fairly easy to do, I did a write-up on this ~4 years ago.

Someone might have retrofit a basic panel in the seat, have you checked?