Cot waking bub up

My daughter is 8 1/2 months old and over the last couple of weeks she has started moving around alot in her cot at night which seems to be waking her up. She gets herself stuck in a corner or up one end and can't get herself back to sleep because she's uncomfortable. Considering she's slept 12 hours a night since she was 7 weeks old, this is annoying to her and also a big shock to my system because I am being woken up a few times a night! Has anyone else out there experienced this? Has anyone got any solutions? She sleeps on a matress on the floor for her daytime sleeps and loves this. I am wondering whether I now have to sleep her on the matress at night too? Is there a problem with sleeping a bub on a matress all night when they're still so young? Any suggestions would be appreciated!

My daughter is about to turn one and she stills moves all around the cot. When she first started doing this months ago she also woke up but stopped waking soon after. I think they just need to learn how to untangle themselves. Even now she will still sometimes cry out but only for a few seconds and then you can hear her resettling herself. I would suggest to keep your daughter in the cot at night because if you put her on the mattress she will probably still move and end up on the floor - waking you up!