When I photograph babies, I use a space heater to make the area around baby very cozy and warm. For many poses, the baby is naked or just in a wrap or diaper cover. If the baby feels chilly they’ll be uncomfortable and fussy. Keep in mind, they are used to the heat of Mom's body temperature, and because they cannot regulate their own temperature we need to help them out.
So I like to suggest to my clients that they keep your home at a comfortable temperature (between 20-22 C). Be careful not to over-bundle your baby. When babies are too warm, they will be uncomfortable and it can also be dangerous. A good rule of thumb is to dress the baby with one layer more than what you are wearing yourself.
A cozy sleep environment will help your baby sleep well. I recommend using a warm flannel fitted sheet for your baby’s crib regardless of the season. Soft one-piece footed sleepers will help your baby stay warm from head to toe. For an extra layer, put a onesie or undershirt underneath the sleeper.
Babies like it warm, so give them what they want and you will get what you want: some sleep!