Arching back??

My little guy has started arching his back/throwing his head back in protest if he doesn't want to do something. It started with the car seat (totally fine once he's in it but oh boy, getting him in is an adventure!) and now it happens with diaper changes... Anyone else?? He's usually a happy, agreeable little fella so this has been an adjustment! My best guess is that he's starting to want to be independent and assert himself. Wondering if it's just us?