100 is normal especially with the A/C on. Even talks about that in the owners manual. 120 is overheating. If 110 was an issue red would be at that mark. Remeber these cars are made for speed, idle doesnt do as well as movement. Age is a factor but 100 is normal with A/C on. Compressor steals power causes load and uses power and creates its own heat and moves heat that transfers to the block.

If you do a search here and benzworld.org youll see alot more of it. Since its warmer out the temps just get higher on the gages. Its gonna happen.

If you want it to read lower try cool harness which tricks the Aux fans to come on sooner to keep it cooler.