Sounds like a wiring issue IMHO. Does your high beam work similarly or does it work all the time? If the HB works all the time you should be able to rule out the fuse as well as narrow down the potential problem to the separate wiring for the LB.
I would star with the headlight itself and trace backwards. Start with the stabilizing clip, if that's gone the light could theoretically wiggle back and forth which would cause intermittent issues. Then follow wiring and see if there is any chafing anywhere. Also have you checked the bulb itself? If it is older it may have an issue inside and be ready to burn out, you should be able to check that just by pulling the bulb. Just some thoughts. Good luck with tracing it.
Sent from my Motorcycle iPhone app