Any tips on getting your baby to sleep on his back? He doesn't like to be swaddled and he startles himself with his arms when sleeping on his back.

He gets startled by the slightest sound! It's so cute though lol
I swear it feels like my baby is having a seizure in my belly. It startled me out of my sleep. Should I call the ER? Now I feel small thuds and movement. I'm nervous.
Gotta hate baby hiccups!
Just when I changed my lo's diapers, fed him and managed to put him asleep, the hiccups come :( they startle him awake and they've been going on for 10 mins now.