Got enough coolant? What's the condition of the coolant (and the interior of the radiator)? When is the last time the system was thoroughly flushed? Is the aux fan kicking in?
On mine the temp was starting to climb in traffic. I had the radiator boiled for PM and put new upper/lower hoses and 50/50 mix in (MB coolant) and Water Wetter. Temp now sits nicely just a shade above 175. Should do fine when I run it to Las Vegas at the end of the month.
I would start by checking all of the above first. Possibly even change the T-stat for GP.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.