It does seem to be worse when cold, as far as I understand it, is generally caused by oil drag between the clutch plates and also between the gearbox bushes, gears and shafts when the oil is cold (and therefore thick) when the oil warms and thins out then the problem seems to go away or at least improve.
It should be remembered that the gears in a normal motorcycle gearbox need to be rotating at *slightly* different speeds (or one slightly moving and one not) in order that the dogs on the two engaging gears (or dogs and holes) on the same shaft can slide past each other and find a space to drop into, if the dogs hit 'head on' then the two gears cannot engage with each other, and feathering the clutch can rotate a gear enough so that the dogs then engage.