1999 Renault Megane Auto light comes on.

Hi,
I have recently bought this car and the auto light has come on twice in the space of 4 weeks. When it comes on i loose all acceleration power. When I stop and turn the key off and on again, the power comes back to normal and the light goes off. I don't have a manual for it, so cant check what this light is for. Any suggestions?

Thanks,