A sleeping bag will help the issue with getting stuck between the bars. But ultimately you just need to let her get used to the space and she will eventually stop banging her head.
Get a sleeveless sleep slack it will make her comfy and warm and also there won't be any risk of her getting her legs stuck. My son is 6 months and wiggles and moves a lot but I don't pick him up. He just falls asleep on his own.
9 months on and I still have this problem 😫 I miss when she was a newborn and slept through.
My son moves around so much in his sleep he practically ends up sleeping upside down but he’s in a sleeping bag so his legs don’t get stuck x
I have breathable mesh covers on the sides of my cot to prevent my little one getting arms/legs stuck x
A sleeping bag will help but ultimately they get used to it eventually and it’ll stop 😊