Sometimes there is just too much going on when you are watching TV. Even if it feels mindless, your brain is still processing and maybe getting overstimulated.

I tend to choose shows that don't have a lot of movement, flashing lights, or a lot of overlapping sounds.

I know what you mean about vegging out. It feels nice to just feel like you are relaxing, but your brain isn't.

Maybe just try little bits, and then have quiet. Or just listen to music or something that makes you feel calm.

Good luck