hi i have a skoda octavia tdi 51 reg and when you restart it the revs go up to just over 10rpm , then you drive about a mile then it drops to wat it should be ,never does it in normal driving it just everytime you restart it now it used to do this now and again but its doing everytime you resart it now . any ideas

I suggest moving this to the mk1 Octy forum if you have a 51 plate, is the engine the same as the mk2?

I guess egr or temp sensor or something could be to blame?

Yep this in the wrong forum, report the thread and ask a mod to move it to the right place.

As regards the problem, it could be the coolant temperature sensor (CTS). Getting the car scanned for fault codes would be useful.