Oh the joys, we have these already although most of the time he is on his back and kicks out like a crazy mofo... It's those moments its like what are you doing, you are hurting yourself. I hope this stage passes rather quickly, how old is your little girl?
Our oldest is 6 and this one is 1.5. So it is the crazy tantrum stage...
This one is also a bit more energetic than the first. The oldest was really calm and rustig (brain is too tired to remember the English word...). This young one, she struggles like crazy, like you said, it's almost like they are going to hurt themselves!
Usually, we just leave her alone and ignore her. When she realises no one is paying attention, it suddenly finishes...
We are learning to do this but its so hard to watch, it makes me cringe, but I have to move away cause when his in a full fit he hurts me.
It would have been nice to work our way up to this stage from newborn but I'll take what I can get lol.