Have you seen any changed behaviors in food, tooth grinding, behavioral or energy. Just to rule out that it’s health issues.
Just look like he fell asleep while being a loaf bread. Often when my bunny do that he will tip over after a while and fall off the things he was sleeping on. I always laugh at watching the panic when he falls and try to cling to the his small hide house. While my other bunny will sleep like that but it happens rarely he prefer flopping and laying like a dead bunny.