I am afraid I don't know the solution to this yet. But I will share with you what I know.
I am having exactly the same problem. When I leave it alone for half an hour it goes away! And it doesn't even store a fault code for the technicians to see. Once when I had this problem I called the AA and they connected their computer and found a fault code with the description P0120 'Throttle/pedal position senor switch A circuit'
I took it to the garage(Bridges Renault Maidenhead) but they couldn't find any fault with it so I had to take a day off and drive the car all day to get that problem again. Then I showed it to them and they charged about 300 pounds (43 for looking at it and 263 for 'fixing' it) and told me it was fixed.(they changed the
) But I had the problem the very next day! So I am going to take it back to them. I will continue to update my story.
So far I have noticed the following things.
It happens after I have driven the car for about at least half an hour on a motorway. But it never happened while I was on a motorway.
It always happens when you are on a low gear (first second or reverse)
If I stop the engine and take the key out and wait about 15 - 30 minutes it goes away. But some times it takes a bit longer for the car to get back to normal.
I will let you know if I find anything more.
And you might be interested in this one as well
This guy has said 3 garages have failed to fix this problem!
We are all in the same boat I think.
Hope we find a solution to this soon!