If you have the adjustable electric clutch, the one with the three bolts with springs above them, take a feeler gauge and insert it into the slot next to the bolt, between the clutch plates, sometimes take a little wiggling to find the space between the plates, and set the clearance at .012 all the way around and see if that helps.
If that doesn't fix it, the clutch may be going bad, or you have a bad wiring connection someplace between the switch and the clutch.