Engine running issue

[MaverickTDi]

Something that I've noticed over the last few months is on cold start up the engine revs seem to fluctuate on start up. It's turns over fine, after 2-3 cranks, but when running the revs bounce up and down in the 1-1.3k range. This only last for approx 3-4 secs. When the engine is warm it starts up fine with no fluctuation.

Any ideas? Or is this 'normal'?

Engine is 1.8 5v non-turbo APT code.

Cheers.