2007 Mercedes-Benz GL450 electrical system problems

I was driving in my son [xxx] to his school in wayne new jersey with my gl 450 seats warmer turned on in both the drivers and passenger seats. I started smelling smoke & thought it was from outside. I opened my window, and smoke started swirling inside my car and started getting thicker within minutes. I try to search for the source of the strange smell - but no obvious clue observed. When I reached my destination I noticed that the seat has burned a hole in my suit jacket back left side.

I was in my 2007 mercedes gl450 and had driven approx. 2 miles with my front driver's seat heater on. I started to notice a strange smell and suddenly the cabin was starting to fill up with smoke. I immediately stopped the vehicle and discovered the left side of the back of my front drivers seat was on fire. Snow was on the ground so I scooped up snow to pack in the fire/hot spot which had burned a large hole through the vinyl and inside padding material.