2007 Nissan Altima • 98,000 miles

My car will not blow any air whatsoever hot or cold, until I have been driving the car for at least 20 minutes, sometimes longer, depending on the temperature when I got into the car. It will not blow at all through defrost, or through the dashboard. But you can feel a little heat come out. Once it finally kicks on after at least 20 minutes, it blows fine and nice and hot. What's making this happen?
December 11, 2013.

Is the blower motor running but you don't feel heat?