MGZT V6 misfire at low revs

[Stephen wade]

Hi need advice I went out in my ZT V6 and all was running fine then when I was parked up on tic over the engine started to sound as it was missing a little and the rev needle was going up/down and when I went to pull off it started to like miss but once it got to 2000 revs it seems to be totally fine I’ve checked plugs and all connectors / connections and all seems ok got over qrt tank of fuel it’s never done it before can anybody plz help or know what it might be many Thanks in advance....