Well you say he isn't stressed, you don't think its a feed responce either... So h*ll your guess is as good as mine hahhahaha.
Ive got some 6 month olds and some 3 month olds and there's no rhyme or reason why they start to spring around, they're are letting me/my shadow know they are not to be messed with... It's basically they're only defense besides rolling up in a ball and hoping... And like you said when I pick mine up also all that non sense stops. I see it as "all talk" so to speak