It may be time to replace your Pollen filter, especially if you have allergies. This is the filter which brings clean air into the cabin of the car, and it should be replaced on a regular basis. Porsche recommends changing these at 15,000 miles, and every 30,000 miles after that (i.e. 15k, 45k, 75k, 105k).
Fits all 2009-2016 Panamera models, file photo shown.