A couple of things that I'm thinking is;
Coolant fan not turning on. If you turn on the A.C. it will turn the fan on if it is operational.
Air lock in the cooling system. Let engine cool down, add coolant directly to radiator while engine is running. USE CAUTION
Could be numerous other things. Thermostat, water pump, etc..
Maybe someone that has the same car and has had the same problem will chime in.