This has happened to me twice since last night and has been an infrequent occurence before then. The speedo will go dark between the surges when starting and the tripometer will reset. The battery is new as of last spring and I've kept the trickle charger on it most of winter. I have been riding it recently as well.
I would almost put a volt meter on the battery when you start it and see the voltage. Sounds like it's lack of voltage. Maybe loose or bad connections, power and grounds