I have an Astra H 2.0 Turbo 
Going home from work yesterday the car started playing up. I went onto the motorway and went to accelerate only to experience a juddering/ hesitation and no real power and the exhaust emmisions light came on.
I nursed the car home and by the time I got home the car sounded like a Subaru Impreza.
Took the car to the garage today and the ODB port on the car isnt working so no diagnostics. I kept the car under 2000 revs and by the time I got home I decided to give the right pedal a tickle........all is fine no juddering, pules like it should.
Went to go to work tonight, started the car and it is running lumpy again, juddering/ hesitating/ kangarooing. I pulled over, stopped the car and restarted the car...........all is fine again, smooth, plenty of power.
Is this a misfire, problem with the plugs or coil pack?
Any help will be really appreciated.