Have I got an auxiliary water pump?

[Muleears]

I was driving my new-to-me '05 X5 with the 3.0 in the snowstorm in Virginia today (it did wonderfully), I noticed when I stopped for more than a minute or two the heater would stop working. Fan would blow but the air was cool. In my old Benz there was an auxiliary water pump that kept coolant moving when the motor was running slow and the regular water pump wasn't moving much. I notice when looking for parts, there is an electric water pump also available. Is this for an auxiliary system of some sort or is it like the one on my benz? Either way, why is my heat going away when I sit and idle for a few minutes? Cooling system is full. Maybe need a burp? Help me out. Thanks in advance.