How do I stop my brakes making this noise/juddering?

Hi, looking for some help with the brakes on my bike please.

It’s a GT Carbon Sensor ST. The brakes have recently (after about 100 miles) started to make the noise you hear in the video (I’ve heard it referred to as turkey gobbling!) and juddering under hard braking.

The front is worse than the rear, but both brakes are doing it.

I had read that it could be the spokes of the disk touching the pads, so I’ve tried shimming the pad holder out by a mm to move the pads further out towards the edge of the disc. This did help for a few miles but then the issue returned.

I’ve retightened everything I can see.

Is there an obvious cause for this? My previous bike had V brakes so I’m new to discs.