Scratching head while sleeping

Hi im a FTM and my baby is 4 months old and she love to scratch her head while sleeping. She will stop once she is in deep sleep but it does distrup her sleep. I have to hold her arm or hand to stop her from scratching. She doesnt have an ear infection or cradle cap or any sensitive skin. When she was 2 weeks old i did shave her head as psrt of religion and now her hair is growing well and healthy. Is it because her hair is growing longer thats why its itchy?Does any mummies experience time before? What should i do? Is it normal? #1stimemom #firstbaby