Hello and welcome to Just Answer.
Is your vehicle an E46 or E90 body style?
Is this a coolant level light?
Ok, a 2006 325 is an E90 body style. This is the engineering designation given by BMW. It is how the vehicle body styles are identified.
The warning you are talking about is the overheat warning.
Is there coolant in the overflow tank or is there a leak you can see?