'99 Accent CSI Strarting prob's after driving
 

Hi all,I urgently need some help!!My 99 accent 1.5 csi will start smoothly in the mornings and the afternoons after work.But as soon as I have to stop somewhere and switch the vehicle of,it wont start again!!After the humiliation of sitting in the vehicle for an hour in South African weather and cranking it every now and then,eventually it will start.I have changed the fuel filter,no good,fuel pump,no good!I have read about a similar problem somewhere on this site but cannot find it again.
I had the computer plugged in at a mechanic,he couldnt find a problem.