2.0 CRD erratic cold idling in start up. help.
 

Hi everyone my diesel Sebring has a very erratic idle on cold start up. It fluctuates between 800rpm and 1200rpm it seems to do this for about 3-4 mins.
If i try to pull off whilst this is happening the car seems to struggle and the at times it has even stalled.
Is it supposed to be this bad?
Also a bit of a daft one but when turning the car off i hear what sounds like the stereo in it's last death throws.
A mechanic said it's the engine releasing the stored up pressure and all new diesels do it. Is that right? does anyone have this?
Any help greatly appreciated.