service engine light on 2006 Mercedes-Benz E350

what does it mean when service engine light is on?

Asked by for the 2006 Mercedes-Benz E350
This is likely a check engine light:

However, your car has a very advanced maintenance minder that tells you when you are due for service, so you may just be due for scheduled maintenance. Either way, it's time to visit a shop for service or repair.