you just said "I know they're nocturnal"....nocturnal means active at night, diurnal is active in the day. I'm going to assume you mean diurnal, because that's what beardies obviously are.
In regards to being skittish, well, he's just a little guy, and sitting with you while you watch TV when it's dark out (signifying the need to sleep). No offense of course. It's normal for most beardies to still be a little weary of the owners even after years of being taken care of by them. The little thing probably was just scared because it was dark, there were noises and light coming out of the TV, and he wasn't in his cage which is probably where he feels most secure.