Electrical shuts down

Vehicle has an intermittent electrical short. Sometimes the head lights dim briefly, sometimes the engine stumbles briefly, sometimes the radio or speakers pop and go out briefly, sometimes the ABS and brake dash lights come on briefly. All have happened independently and together, in various combinations, as well as all at once. After this brief hiccup, the vehicle continues to run normally with no codes or warning lights. Of course, the dealer can find nothing wrong. Help?