Swaddling
Your baby has spent nine months tightly wrapped inside the womb. Then suddenly their arms and legs can go everywhere and they have no idea what to do with them.
A firm swaddle replicates that sense of containment. It also helps with the startle reflex, which can wake a sleeping baby just as they are drifting off. A well-wrapped baby is a much calmer baby.
Wrap them snugly with their arms tucked in. There are lots of swaddling tutorials online and a little practice goes a long way.