Most Mercedes keys are dealer-only keys. There are some that are not but you would need to call to discuss.
There are other ways to program keys to most Mercedes, but we don’t like to do this as the parts are very expensive if they go wrong. My advice for the remote/fob keys is to go to the dealer.
Do not buy second-hand Mercedes Benz keys from eBay or scrap yards as these keys cannot be programmed into another car. Each key has a transponder chip which can only be coded once after which it is locked out.