Throttle trouble???

A light showed on my dash saying there was a problem either with the throttle pedal and sensor or the throttle body. The pedal was changed the fault re occurred. The throttle body was changed the fault re occurred. The car drives like a dream and then suddenly the light comes on again the car goes into limp mode and the temperature goes up.
Switch the engine off and start again the fault has gone and the car drives normally and the temperature drops until the light shows again. It just randomly happens.
Can anyone offer assistance?
Please.

Sorry

I have a Vauxhall Astra Club 1.6 V8 02 plate