Have you checked your Grounds? I had a similar problem where if I went over a Bump/pothole my lights would flicker and sometimes my Radio would shut off.
I fixed my Problem but Sanding off some of the paint under where the grounds were and scraping off a little rust from the Nut and Washer holding it on. ever since then no problems.
If it turns out to be something else you might want to make the switch to another lighting system such as an LED Rope with White face Gauges, it cuts down your power consumption and really makes the difference at night.
