Curly hair is special and needs to be cared for while you sleep.  Cotton, nylon and other fabrics will actually pull moisture out of your hair and cause frizziness.  This means that your sheets, your pillow case, and your towel are party to blame for your frizzy hair. 

If you are going to do an overnight condition treatment, apply that to your hair.  I find that a small amount of shea butter, hemp oil, or cocoa butter worked into my hair does me a world of good.  Once you have your overnight treatment worked into your hair well, then you have some choices. 

Many of us sleep in what is called pineapple.  Turn your head over, and make a big pony tail on the top of your head with a scrunchi.  If your hair is too long this might not work well for you.  You might need to go to a banded pineapple.  You make a regular pineapple and then apply more scrunchies to the hair about every 4" or so to keep it banded. 

Otherwise, you can apply your satin sleep bonnet, do-rag, or just a pillow case and get to snoozing.