What is the correct way to say this..?

4 anni fa

When my small son goes to bed his granny covers him up with a duvet, but he always uncovers the duvet and that’s a real problem. So, his granny puts socks on him not to get cold at night. I wonder what is the correct (common, natural) way to say to him the sentences below in English?

“Why are you always unwrapping yourself? Wrap yourself up with a blanket and sleep!”