Lot of possible reasons. Some of them very stupid, even though I mention it here, sorry:
1. Thermostat regulating the cooling fluid flow - works correct?
2. Enough cooling fluid? Not leaking from somewhere?
3. Level of engine oil? Its quality? (If dirty or low oil, heat can not spreed into oil - oil is cooling subsatnce as well. If low oil level - you know what, engine is not lubricated etc.)
4. Water pump works correct? No pump, no water circulation.
5. Any dirt in the water circulation system? Piece of rock, shred of rag, maybe some sediments (can figure out only after disassembling the system = lot of garage work).
I had one friend who complained about his mazda MX3 quick overheating. My first question was, if there is cooling fluid and he told me "Of course!!! - I was in the garage yeasterday evening and fluid was refilled." The engine was hot and smoking badly after 3 mins of calm slow ride. Next day he called me with curious finding - there was no cooling fluid at all, was leaking out from the radiator.
Thanks for contacting Fixya.