Could be a bad headlight switch, a couple wires in mine were starting to melt together for no apparent reason a long time ago and the inconsistancy of the lights was one thing that happened. The other thing it could be is your multi-function switch, I recently found out that this stupid thing has some control over the headlights. Mine would flicker semi-rapidly on and off and finally wouldnt come on at all (happened at night, I was thrilled as you can imagine). Next time your lights go off try to hit your brights and see if they work, if they do its a strong possibility that it is your multi-function switch.