I had this same issue and it was in the shop a long time for troubleshooting. But the good news is that it's an easy fix. The issue is low oil pressure to the clutch area (mine was measured at half of what it's supposed to be), causing the plates to be not wet enough when you pull out cold for the first time (or even after idling for a while). After a few minutes of riding, all is wet and good, but the initial shudder on my bike was very disconcerting.
The fix is an oil-pressure adjustment screw very near to the front sprocket. The service techs should measure the pressure in the clutch compartment and adjust this screw to
spec. They also blew out my oil circuitry with compressed air, in case any debris was blocking things, but saw nothing. Immediately after this screw had been adjusted, my clutch plate engagement has been pure butter ever since. (Note this is a totally different issue than the soft clutch lever issue caused by air getting into the hydraulic circuit.)
I wrote more info about this issue on this forum many months back, but can't find the threads.
