As said above the electrics should be checked especially the roof that's a must, the service is covered by the OBD for intervals so if it's driven in a certain way that then tells the computer when to ask for a service, as long as it's done at Merc then at that age any warranty claim should be straight forward. Most of these are ex lease cars, so either a company car or a fleet hire car, I've had a few and the engine etc seems good at this age, these newer Mercs seem solid really.