I drove past a car that had its headlights flickering about 15 times every second last year. No clue if it was intentional but it was distracting as all hell. (and probably dangerous to epileptic people)
This is typically someone who installed LED lights in a car that was designed for incandescent most DRLs run at a lower voltage than when the actual headlights are turned on. So when you run lower voltage to run those daytime running lights when using an LED bulb instead of filament that wasn't meant to be dimmable they Flickr or flash.