I put about 2 cups of water in and all is fine. You are correct, it didn't
need much.

Thanks

your coolant is probably just at the low level mark in the coolant
expansion tank.   The motoring you usually do will heat it enough and
have it expand to the point where the coolant float will no longer
signal low coolant.  There are two types of coolant, propylene glycol
and ethylene glycol.  See which your bimmer uses and when purchasing
the coolant type used in your car make sure it adheres to aluminum
protecting standards, you neednt pruchase special bmw coolant.  Your
owner's manual should specify which one (propylene or ethylene).  If
still unsure the best advice is to top it off with a lil water.  Any
coolant a car uses is still mixed with water and if unsure of the
coolant type water is best.  happy motoring

My low coolant light has been coming on at first start in the morning. It
only stays on for a short while (about a quarter mile of gentle driving)
then it goes out and doesn't re-appear all day. The temp gauge never gets
hot. If I let it sit most of the day after the initial start, it may come on
for a few seconds. In essence, it only comes on when the engine is cold.

My dealer said to just top it off with "regular green coolant". What would
that be?

I was under the impression that BMW's used some kind of special coolant.

'05 325i