l have just recently bought used Suzuki Grand Vitara 02 plate.
The red temperature light comes on now and then
Even when the engine has first started to run
Any idea why this is happening?

Much Obliged

Without wishing to state the obvious, probably because it is overheating! You could always hope for the problem to be only a dodgy teperature sensor, but if you've just bought it, my guess is that you've just discovered why the previous owner wanted shot of it, sorry!
If you bought it from a garage, take it back, but otherwise, you still need to get it sorted since if it is overheating, you will do some terminal damage to the engine by driving it.