AC/HEAT BLOWER STARTS AND STOPS. BUMPING NOISE WHEN STOPPED

Trying to see if this is a simple fix/if anyone
knows....
The ac/heat blower in my 2005 gmc yukon simply
works when it wants and it's very rare when it does.
Getting hot need some air. Checked fuses water
level is fine. It might come on a few days out of the
month. Just hearing a simple bumping noise when
the switch is on but no air blowing. We can survive
while moving because there's air coming in from
the vents. Yes it's cold air but very light from simply
driving down the road.