E90 320d rough start

Hey guys,

Needed some advice.

I have a 2006 e90 320d. The car has 230000km on the clock. I have been, since last month parking the car outside underneath a shed and no longer in a garage (due to moving).

I have noticed now when starting it in the mornings or for the first time for the day, it starts rough with like a knocking pulley noise from the engine and the Rev needle moves up and down above 1000rpm. It does for about a minute and then it is back to normal.

Any idea what could be causing this?

Thanks in advance.

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