All lights flashing while driving.
 

I am having a problem with my lights. they flicker while sitting still but when I am taking long trips they flash. They don't go completely off but dim and bright melodically for nearly the entire trip. I have had the battery, alt., and starter checked to no avail. I have looked through forums and recalls and could find nothing on this issue. Someone please let me know what to do to fix this problem.

P.S. this includes all the interior lighting, i.e. dash and panels.