Waking up with knotty hair is usually down to friction. Cotton pillowcases can...

https://www.bright-bookmarks.win/minimise-overnight-friction-to-protect-your-hair-cotton-pillowcases-can-cause

Waking up with knotty hair is usually down to friction. Cotton pillowcases can be rough, so switching to silk or satin helps. For extra protection, secure your hair in a loose, low plait before bed