hi guys
have a 2.0 tdi 2010 a4, on start up especially in the cold im getting a very violent judder on idle, feels like a misfire but when driving it smooths out and runs fine.

There are no warning lights on the dash so through out my theory of it being the glow plugs. sometimes there is a knocking noise on start up too coming from the drivers side of the engine but again it goes away when driving etc.

Could this be some kind of valve that is disturbing combustion?

any help is dearly appreciated
thank you