HI there, I've noticed that my headlights sometimes will intermittently dim for half a second for no reason. I saw it first about 3 years ago. It's as if they are half - blinking. It once repeated regularly at 5 - second intervals for about 10 minutes. Usually it's just once or twice on an hour - long trip. I'm thinking either electrical system, battery, or maybe alternator. I would appreciate any advice on this. Thank you,

Ulric Schweizer