One thing I’ve learned as a pediatrician and photographer is that babies need to be safely held but they each have their own preferred way to relax.
Some like to lay on their side, others prefer the back. And when they get old enough to roll over, they often want to be on their tummies. I really like that. I enjoy capturing a child in their naturally comfortable position. Like with everyone else, the best photo of a person is when they look like themselves. Not wearing props or in an unnatural position.
During my portrait sessions, parents are always right there to help entertain their wee one but also to keep wiggly babies from rolling onto the floor! And sometimes it’s non-stop action.