Urgent starting problems

I'm assuming yours is a petrol model like mine. I've had the starting problems several times, and and also the problem of the revs sitting really high. Dealer cleaned and reset the throttle bodies, though the resetting didn't always work first time (car sits at high revs for several hours/days: it's meant to re-adjust itself gradually, though dealer couldn't say how long it would take), and the car had to go back in.
Also had the throttle bodies replaced under warranty when the problem first occured.
The last time it happened (revs would intermittently stick at about 5000rpm) I tried the resetting of the throttle bodies trick (turn ignition on but don't start the car, let it sit for 2 minutes?, switch off and then start up and bodies should have reset) but it never really worked for me. There's info about this on here if you do a search, but also lots on the MkIV forum. If the ignition trick doesn't work I'd take it to the dealers. Think at least once the dealer also replaced the engine temp sensor to cure the starting problem.

Hope this helps