Just purchase 02 ml500 last week. Notice temp goes up to mid level or a bit higher (between 80-90). Any advice?

 

After a nice run or sitting in traffic, Mercedes tend to do that and from what Mercedes has been saying it is normal for it to happen. Just dont let it go over the red line.
If the temperature rises quickly ver rapidly and dont stop at 90, either there is no coolant or not enough or the thermo stat is stuck closed but either way, in those cases the car would go up and beyond that 90 range and cross that red line.

 

Thank you Blackwolf. Just went to check coolant level this morning (before driving it) and not sure ifit is low(it's below the line where it saids cold level). I think I am going to add some coolant later.