Upon trying to start up of my golf mark 4 1.6 petrol, it makes a very uncomfortable knocking noise, shortly after that it tries to start and idle on its own. This happens for around 15 seconds, after that it becomes normal and ticks over like an engine should sound/behave like.
It's hasn't been running smoothly for around 6 months, although I thought this may be just down to the cars age.
I thought it may have something to do with the spark plugs but most probably wrong.

Your advise and help is really appreciated, thanks
Ben. East Sussex