How do you remove mass air flow sensor on a 2000 Mercedes Benz S500?

Usually a short plastic cylinder in the air intake pipe, just after the air filter- will have an electrical connector and a wire on the side of it.

I'm not 100%, but I think on that model (220) the air mass sensor may have had a built in control unit, remember them costing quite a bit....

Just take it out and give it a clean, theres a piece of metal inside that acts as the probe which is probably just dirty....worth a try....