Not reving when starting it warm 1.9 dci

[Craigo]

Hi, can anyone help?
I have just bought a 54 plate 1.9 dci Megane, When i start it from cold, it will run all day long, but if i switch it off and try starting it again while it is hot/warm, it will start but it just stuggles to iddle and i have no throttle control.
The air bag light is also on and so is the service light. The car has been stood for 4-5 months, but runs A1 if it is started from cold. Any sugestions welcome, Thanks.