Clenching belly while shivering.

Brittany • Our baby boy born July 2016 💙 Our angel baby was taken Oct 2018 💔 Our Rainbow baby girl born Aug 2019 🌈 Currently TTC 2022
I'm 16 weeks. It's like 5° outside. And been snowing. In my car I've noticed I'm clenching my abs while shivering. Is this a bad habit for baby? I keep trying to relax the muscles but they clench up again as soon as I quit concentrating on them.