Headlamps Flash On and Off While Driving

I've had this issue before on a 1969 Dart 340 Swinger. Where the headlamps would not stay on. They just randomly flash on and off during the course of driving at night. Now on my 1968 Barracuda I'm encountering the same thing. What would cause this? Is it a short somewhere? If so, Where? Has anyone else encountered this before? Maybe I need a new headlamp switch?How do I even begin to investigate this without going into an expensive automotive electrical shop?