Do you see any leaking?
How many miles on car?
When were radiator hoses last changed? or have they ever been?
Does turning on heater show a drop in temperature on the gauge?
Overheating in city traffic? motorway traffic? both?
Any recent engine work done? exhaust work? brake work? body work?
Only overheating with air conditioning on?
1) Low coolant level, or not a 50/50 coolant mixture, not enough water in coolant
2) Thermostat faulty - not opening - you should feel upper radiator hose get hot after operating in warm temps
3) Radiator core blocked - mechanic can use heat sensor to check and see if proper flow is gong through radiator
5) Cooling fan not working, fan behind radiator should come on when car is running for a few minutes when stationary and hot.
6)Inaccurate temperature gauge sender unit
7) Air-bubble in cooling system
8) Radiator cap is faulty - they should be changed every few years or after an overheating episode.