Check all the grounds on the bike. There should be several. Wire brush them them bolt/screw them back in place.
Also try disconnecting the headlight and work the switch from low to high and see if it does the same thing. As said prior check the fuse box and make sure the circuit breakers are clean and have 12 or more volts in and out while under a load.
You know what? this right here makes me think a circuit breaker is popping and resetting (...In another 30 seconds, if the key is left on,
everything electrical will turn back on and the vehicle will start
normally...)
I would look at the voltage in and out of the breakers while the High beam is on.