I had similar problems with my clutch - on infrequent outings, trying to pull away, nothing, then would suddenly grab and jolt the bike forwards, or stall it. Seemed ok on the move, and when being used regularly, so I put it down to one of those things that just happened when the bike was rested for a few weeks. The problem got much worse a couple of years ago, and every start up was a gamble pulling away. Bleeding the clutch made no difference. I removed the clutch slave cylinder assembly from just in front of the gearbox sprocket cover, to find the clutch lifter rod (which runs across the width of the engine) siezed in place with a mixture of grease and dust, as well as lightly scored in places. Removed the rod, cleaned it up and polished it, as well as degreasing the hole it fits in and thoroughly cleaning this with a bottle brush and solvent cleaner, before reassembly with a fine coating of light oil. Since doing this, my clutch has been smooth, as well as a lot lighter to operate and I have had no further on/off issues when pulling away. Simple job to do, worth repeating every couple of years to ensure smooth clutch operation in the future
Even getting a dealer to carry out this work would pay for itself if it saves a costly and embarrasing low speed drop from doing damage to bodywork, radiator etc in future.