Weird noise when I brake

It sounds like I’m pumping the brake but my foot is motionless. It doesn’t do that all the time, it’s off and on and the engine doesn’t have to be running.

At first I thought it was a quirk of the cold because it quit doing that but it was warmer today and now it’s doing it again

Any ideas what the issue is? I know brakes get noisy when it’s cold but this isn’t like any YouTube video I’ve ever see (it’s a new car. 2013 Chevy Silverado, 160,000 miles)

Thanks you all