I noticed that, too. I watched the video now available and all that fiddling about in his chair done by BW3 seems to take place when the "charges repetitions" are addressing Frankie and Hannah G's murders. However, I watched BW3 closely and he doesn't seem to be listening to or being affected by a word the judge is saying at that point. His attorney seems to be explaining something to him. Other people might see it differently and I'd be interested if they do.
One problem is that the camera person is filming those in the benches when whatever is happening for BW3 begins. We don't see him from the beginning of whatever seems to be bothering him, imo.
(And he may not be bothered because he seems to have a sort of naturally grumpy face so it's hard to gauge what he might be feeling.)
I have a hearing issues, and I noticed that BW3 had his lawyers to repeat things to him several times. I wonder if he does have a hearing issue and that is the reason he seems to not pay attention more.......