My overheating problem in the same model as yours was caused by a faulty radiator fan controller, which is only available as part of the complete fan assembly.

It would work great most of the time. But, when it wasn't working, the gauge would go into the red and the A/C would go out. It happened almost predominately during slow/parked engine running. At speed the problem would usually resolve itself. It is most likely the fan, but there is a slight chance it is the thermostat. Have your dealer check both, as the thermostat is infinitely cheaper than the fan (if you're paying for the repair).

Good luck.