When stationary in neutral it feels like something catches in the gearbox causing the bike to lurch. There is no loud nasty mechanical noise (yet) It managed it the other day after I started it up to dry it after a wash - thought it would throw itself off the side stand

Seems to happen intermittently on a hot or cold engine. The clutch is fine, gearbox seems as rough as it ever was and I'm not riding any different, plenty of oil in it.
Bike has 26k and a FBMWSH.
Any ideas - or is it just the cold?
and will it be expensive - its out of warranty....

Cheers,
Ade.