Welcome to the forum!
I'm no expert in this area, but I've seen some threads with the same complaint.
Try a search on A/C or air conditioning, or vents, etc. Perhaps the solutions outlined on those posts will also rectify your problem.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car