Headlights keep moving up and down on their own

Hello all,

I have a 2012 C4 (B7) VTR+ (no xenons) and recently I noticed that the headlights keep moving up and down at low speeds (I can also hear the headlights adjustment motor working). I don't think it happens on motorways although I doubt I would be able to notice. Is this an issue or is it intended behavior even though the handbook doesn't mention it? Thank you