Roxan310

When I start my 2013 c250 it blows out white smoke

Big Daddy

Cracked head or blown head gasket
White smoke indicates coolant is getting into a cylinder
Dont drive it as more problems will eventuate

Demvang

Starting with white smoke in cold weather is absolutely normal

Darrell Simmons

i have a C350 with similar problem, went into the workshop to have the following done, oil and filter change, air filters changed and fuel filter changed.
Came out and now i have quite dense white smoke from exhausts on start up plus it's very lumpy when i start it up and i have a low rumble/rattle from the engine bay.

Not sure what to do, i feel a hefty bill coming my way.

Alfadude

Did you take it back where you had the work done? If so, what was their response?

From your description that seems like something you would have noticed right away when you picked the car up. This is all assuming the car was working perfectly fine before the service.