Drove the 94 E320 (79,000 miles wifes daily driver) to a party tonight about 4 miles from home and I noticed the temp was creeping up to 120, just under the RED zone. We arrived at the party location just in time. fyi, outside temp is mid to upper 40's.

On the drive home it made it to 110 or so on the gauge by the time I pulled into the garage.

Could it be a stuck thermostat?
Radiator cap?

Any suggestions would be appreciated.

Coolant is MB brand from the dealer, maybe 6 months old.

I checked the radiator fluid level when we got home ad it seemed fine.