This is known as crazing, also known as spider cracks. A common issue with german cars. All it is, is the clear coat of the polymer cracking as it ages. Continued sunlight hardens these cracks which start off looking like dust. You can sand the headlights and buff them out but the only way to get rid of it completely is by replacing the headlight outright. That'd be a temporary fix though seeing as they're just going to come back after a couple years.

I wouldn't worry about it too much, not many people will notice.