When the car is cool, take off the upper radiator hose where it goes into the radiator. Hold the hose slightly higher than the top of the engine and pour as much coolant as you can get into the hose. Then reconnect it (be careful, the plastic radiator elbows are brittle and have been known to break easily when clamped).

You might have to do this a few times, but it worked for me. I don't know where the bleed screw is on my car either (if there is one).

I agree with Cliffmac, if the coolant system was recently flushed by someone who didn't know better, it is possible that the heads did not get filled with coolant and there are now air pockets in the system. On American cars, the water pump circulates coolant through the heads as soon as you start the engine. Mercedes is different. Do a search on it. I think I read a post here about "burping" the system after flushing or changing hoses.

Car should not get to 100C, especially this time of year.
The final two things to check are the air pocket issue, then the fan clutch. I replaced all of my hoses and radiator last year and did not have any issues with air pockets. I had to top off the coolant the first few times I drove the car, that is all.
In my case, a new fan clutch solved my problem. Worldpac distributes a good German aftermarket unit for around $200.00. It's been working great in my car, temp is rock solid at just over 80C.

I have no idea what type of fan cluth it has. I have read about it a little and know it is expensive

And if you get on a highway and do 55-65 MPH it does not go back down at all ? Mine drops back to 70 or less

It will drop a bit, down to 80C or so.