baby doesn't sleep in crib

Cali☀️
My baby is 4 months old and the ONLY thing he sleeps in at night is his auto rocker. Well now he's getting too big for it and he's learning to toss and turn somewhat so I tried putting him in his pack and play to sleep. It's flat and safe. He hates it. I'm assuming he will hate his crib too. How do we transition ??? Help please.