Just remove things around the head. They seem to fall in love sleeping on their belly better. I noticed they sleep longer that way too. We have been sleeping that way for ages now 😁
My baby has done this since she could roll. Initially I tried rolling her back, but she would go straight back over. I've just accepted it as she is comfortable and sleeping well like this.
My little one will only sleep on her front or sides, she’s been like that for months now. I was so anxious about it when she first started but that stopped after a week as I realised she was fine
If she can roll both ways by herself & you're putting her down on her back then no need to worry she's just comfy like that