The British and Chinese long-ago figured out that cold feet make for restless sleep. A hot water bottle is the solution. If you can get past the grandfatherly grandmotherly image, putting one at your feet (wrap in an old t-shirt to avoid the feel of rubber/plastic) will add much to your sleeping comfort. Available from most any drugstore, though I like the British 2-quart $10 version. If you’re married, get two to avoid territorial disputes.
[News to me, but apparently there's a small cottage industry making plush covers for hot water bottles. What, you don't want to use "an old t-shirt" to cover the bottle? A few examples below. -- KKSarengeti The Vermont Country Store]