My 18 month old has started wakening during the night for a few hours at a time. I know this may be a sleep regression or split sleep and something I just have to power on through however I feel he that they are feeling restricted in their sleeping bag and this also could be wakening them. The minute they open their eyes during the night they are asking for it to be off. What can I use instead? The room isn’t cold it’s around 21c maybe drops to 19 on colder nights. Is 18 months too young for a duvet? Can I use a fleece onesie on top of cotton pyjamas?