My engine coolant light is coming on @ cold than goes away my car only has 8,000 miles what's happening

You're just a wee bit low on coolant, as the car heats up the water expands past the low sensor level. Mine did the same thing right at around 8k miles and once it started cooling off. Check for leaks, if you find some take it to the dealer. If not add some more 50/50 mix and be on your way :)

Second what QBallz said. I have had to do this twice in 18K miles.

I have this problem too....
now... do I shut of the car to add the coolant or wait til it warm up to avoid flooding?

I have this problem too....
now... do I shut of the car to add the coolant or wait til it warm up to avoid flooding?
Never shut the car off cold.

Add coolant the next time the car has cooled off. If the light goes off when the car warms up you are just a little bit low, and it won't hurt anything to wait until the next time the car is cool to add coolant (50/50 mixture) to bring the level up to the full mark.