Hi,
My son started banging his head (and feet) on his cot around the same age. Just a month later it has passed. In our case, we thought it was caused by anxiety and attention seeking (due to a very pregnant mummy, then new baby!). At first I was sitting next to his cot trying to settle him but we soon realised that he was not going to hurt himself, and gradually moved to standing outside the room, until he went back to sleep. Now one of us stays on the landing for a few minutes then we leave him to go to sleep in peace - no banging, or waking up again.
One thing to consider is avoiding playing after storytime since this might wind her up rather than down, even though she sleeps initially. The main thing that made a difference for us was giving Fraser something else to focus on - a pillow
- his head goes on the pillow to sleep so no banging :wink: .