Manual says:
illumination while driving indicates an engine fault:
- if car drives normally, arrange a service appointment
- if light flashes and / or car does not drive normally, avoid high speeds and seek immediate assistance
My used to come on if I'd had the car idling whilst fiddling with it, and go out after a couple of decent runs, so I suspect it was possibly something to do with emissions, yours could be mixture related by the sounds of it?