RepairPal Certified shops can diagnose and repair your 2006 Mercedes-Benz SLK350. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
It's possible your evaporator is icing over or the evap temp sensor is faulty. The sensor is more than likely. A good scanner with actual values will tell you what the evap sensor is reading. If you don't work on your own car then use this link to find a good shop near you.
https://repairpal.com/repair-shops
Alex