So when you have a clutch, they will huddle, then wiggle up to each other and then tuck their heads under the other birds and use this method to keep warm. The hen then broods on top and maintains a good temp for them all, and will move away when the huddle is too warm.
What you are seeing is your bird not having a huddle to snuggle into. What you can do is give them a snuggle buddy. A small soft toy - some baby toys are good options because they are small for babies to hold. Be sure there´s no loose parts, threads or buttons. The item needs to be small so it can´t topple over on the chick. Failing finding something small enough, you can use a clean rolled up sock. Roll it nice and tight. Place it near a corner but not touching the corner. Make a small dip with your fish down into the shavings for the bird and his buddy to go in.