This is a very interesting concern.
It is unlikely that a voltage drop is causing the flicker because the headlight ballasts stabilize and step up the voltage.
Realistically the lights are not connected to those systems.
If there was one item I would suspect it might be the headlight bulbs themselves. If you bang (closed fist, not hard but hard enough to vibrate the insides) on the top of the light does the light flicker?
If it is something that happens on a regular basis the dealer should be able to figure this out.
I am very interested in the issue, please post what happens.