engine cutting out first thing.

[Lumpy]

oddly enough, it's just started over a week ago now but on first start fine, stand up, into gear and engine cuts out, restarts straight away, no problem. Only on cold start. I't like the sidestand switch is playing up but only ever on cold start guaranteed. Sometimes, if you rev it the engine will cut but continue running due to revs not dropping far enough. May disconnect switch to see if it is the cause but anyone else had it?