My car is overheating not leaking and swicthing on and off again and again?

Today my ford mondeo overheated and when i put water in the radiator the temprature became fine and then later on it just kept turning off and on it kept overheating. There was no leakage of oil or water
no leakage at all
what is the problem with it
it keep overheating and turning off

This is a very good video on all the things that can go wrong with a cooling system and how to find the problems.

What is the year of your car? If it is older than six years old the cooling system needs to be drained, flushed and CLEANED with one part powered acid cooling system cleaner to get the corrosion, rust and slime out.

Your car should always have a 50/50 mix of Ford Antifreeze (prevents rust) and distilled water in the system. Always fill the cooling system when the engine is stone cold.

If the radiator keeps loosing coolant, take the car to a Ford Dealer and ask them to do an inexpensive *cooling system pressure test which will find any external or internal cooling system leaks.