Baby turning on side

My baby is 15 weeks and we're transitioning her to her pack n play flat and then we're going to eventually put her in her crib flat last night was the first night in the Pack N Play flat and all my all she did was try to roll to her side sometime successful we had to watch him carefully that she didn't work because she doesn't have a very strong head. Was so scary but it seemed like that so she was comfortable but I noticed all night she was trying to achieve that. Anybody else having this issue? What should I do later on her back or her side or just let her do her thing.