coolant light staying on

i have bmw e46 m3 2001 63k the coolant light has been coming on / off for last couple of days so have topped up accordingly & then it turned off now it is bk on coolant level is fine, no leaks (puddles under car when warming up) or cracks around hoses i can c.

Any ideas????

I read the coolant systems start to go around 60K???

Not on the E46s. The E36s need a water pump and thermostat housing at about 60K, and a replacement radiator at around 100 - 110K miles.