Besides hot flashes, fatigue is the most common complaint I get from women in the peri/menopausal transition. I've been there, I remember before getting my hormones balanced and getting healthy sobbing in my doctor's office more than once because I couldn't sleep and I was a zombie during the day. It's miserable! My sleep still isn't perfect (back pain issues and years of not sleeping), but it's much better and most nights I get at least some quality sleep.
Check out this article from WebMD.com about some of the common reasons that women are so tired. As always, talk to your doctor about any sleep or tiredness issues.