Occasional juddering on start up

[Jonnykentfield]

Hi guys,

I have had my A3 8L 1.8T Quattro since the summer and in the last month or so it has started juddering for a minute or so straight after ignition. This isn't every time, probably once every 4 times. I'm think probably start by changing the plugs but does anyone have any ideas what is causing it?

Thanks,

Jonny