Waking up with knotty hair? It’s usually friction against your pillowcase....

https://theaustralianpost.com.au/protecting-hair-while-sleeping/

Waking up with knotty hair? It’s usually friction against your pillowcase. Cotton can be rough, so switching to silk helps minimise breakage. Another simple habit is wearing a loose, low bun or braid to keep your hair smooth and protected while you sleep.