H.W.
My 8 week old girl is doing this as well! Sometimes it seems like she's being super impatient, and it's usually when she's not really hungry. She flails around and trashes her head from side to side, which makes me really frustrated, so I just take her off and move her around. Today I stood up and rocked while feeding and she calmed right down.
I've noticed though that she gets super active right before she falls asleep.