110 to 115 on a hot day 100 F or above while setting in traffic is not as bad as you may think...
Thermostats open full at about 107 or so.. So thats really about 110 for most of to read on the gage..
Most MB fan clutches come in at 104 to 110 so under about 110 the fan clutch is not working..
The electric fans come on at about 100 on low and go to high about 107 to 115.. so if your car is one of those that runs things in the upper limits 110 to 115 is really where every thing really starts doing what it should..
Above temps are from a Mercedes Factory Manual and cover several models so your should be near those..
In general most of the newer cars tend to run 100 ish to 115.. Newer meaning 88 and up...
I would change the Thermostat and change the anti freeze.. Never a bad thing to do any way..
After that you can park the car nose in to a wall so it gets little air flow .. back of garage or side of house on a hot day.. turn the AC on... Roll the windows down so you can hear whats happening... Run the car up to temp at about 2000 to 2500 rpm..
At some where around 100 you should hear the electric fans come on... about 105 to 110 you should hear the roar of the fan clutch kicking in... and soon after.. 110 to 115 you should hear the electric fans kick in to high.. ..
If all this happens at temps some where in that area.. Odds are things are normal..