Yes, I do the same thing.. not actually intense rocking, but, I will kinda move around like that and fidget in my chair (I'm in a wheelchair).
I get severe panic attacks, and my big thing is I start Hyperventillate, and that goes deep into a spiral. Because when that starts, I start to think, "Oh no.. I'm breathing fast again.. this must go away!", then the fact that I don't stop breathing like this, makes me more anxious; so on and so forth. But I'm thankful I have medication to help seize the anxiety before it becomes too bad.
yep i rock a lot too.. I'm always fidgeting and doing something anyway but the rocking or swaying happens all the time. And if i'm in a panic it will turn to full on pacing. I agree it's a nervous energy thing. x