Your body temperature drops as you fall asleep, so it might help to increase your body temperature for a better rest. Some people recommend to take a hot bath or shower, but this never helped me because I would always feel cold afterward...
And then this winter, I bought a space heater. I keep it on my feet when I get cold. It's usually on the highest heat setting, and it works really well... too well. I find myself getting too warm sometimes, and it makes me really tired. This thing has made me so tired that I would actually take naps, and I'm not a napper. Now I have to turn it off when I start to feel too warm.