When I start the car, there is a funny smell coming into the cabin. on 2006 Mercedes-Benz C230

The smell is like a sour smell. I know the cabin air filter is in the engine compartment and I plan to change today. Any other ideas anyone may have. Thanks

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2 answers
SPRAY SOME LYSOL IN AIR INTAKE BY WIPER ARMS THAT WILL HELP AND KILL BACTERIA
Also use lysol spray inside the cabin filter area.