In case you haven't fixed the problem yet:

My X5 has the same specs with 61K miles. It had the check coolant light problem for several months now. Low coolant was not the problem (coolant level was near full when light came on). Sometimes check coolant light went off/on intermittently. Dealer replaced sensor today -- specifically, radiator level sensor, fp-number 17-13-7-524-812 -- and so far the light has been off. Will have to wait and see to be sure since sometimes topping the coolant (even when it was almost full) would temporarily switch the warning light off.

My suggestion: consider getting the sensor replaced.