Lately, nearly all the time on start-up I can hear the blower motor running but there's no airflow out of the dash vents. If I reach under the passenger side of the dash and give it a good whack the air starts flowing right away. From time to time, though, the air won't be cool and I have to shut off the ac and turn it back on again and it'll be cool immediately. Is there a known issue of blend door/vent actuators that might be causing this? Possibly a blower motor fan drive issue even though I can hear it running? Any input would be appreciated.