Got the coolant level low message for the first time myself a month ago and it just so happens it was pretty cold that day. I had the car in for maintenance on that day and they just topped off the coolant. No errors since. Just top it off and you might not have an issue anymore...
2008 550i Sport-a.k.a. Hot Kraut Garbage
2006 Corvette Conv, Z51,6sp (wife)
2007 Honda CBR1000RR Sold
2005 Triumph Daytona 650 (wife) Sold