Sounds normal to me. If the temp goes over 95 then there is something wrong. I would have the breaks checked ASAP just so you know the condition. I am not sure if your model has wear indicators or not. All of mine do. If your car does have the wear sensors and there is no idiot light on then dont worry until the light comes on.

If you have a Heater / AC control that is the size of the radio with a display in the middle, the procedure below will work. If you have 3 knobs it won't.

While the car is running, press and hold the REST button until the display starts to flash 01 and some other number. Press the + button on the fan speed until you see 05 or 06 ( can;t remember ) This is the coolant temp in degrees F. 197 is what my 97 C280 and 97 SL320 will see on a hot day with AC on. To clear the data function either turn the car off or press and hold rest again.

80 C is 176 F and kind of cold.
85 C is 185 F is about right on an average day
91 C is 197 F

A coolant change is a good preventative measure as would be a thermostat. With the age and miles, it is reaching the end of reliability.

You really need to find a trusted non chain store shop and have them care for the car. Chain stores are usually only interested in taking high profit margin quick turn over easy work. ( Brakes, tires , wiper blades, battery, hoses )