If I turn off my 1999 Sportage after it has warmed up it won't restart for at least 20 minutes. I have been stranded at the petrol station and several other inconvenient places when trying to get odd jobs done quickly. Any ideas? The car is currently at the mechanics but they don't think there is any problem with it. They don't seem interested and haven't tried driving it, they have just let the engine run on its own. They have looked at the fuel line and the electronics but say there's nothing wrong with either.

I do not know if your problem was solved..but a failed/ailing crankshaft position sensor (left below, near transmission housing)
http://www.geocities.com/lmp4203/kiasport/cam_crank_sensors.jpg

behaves like that, and not just on SPortages.
If in the mean time your problem was solved, plese inform us of the solution: it can help others.
Sorry your first post was overlooked for so long.