There’s all sorts of scenarios where Windows won’t actually sleep when you tell it to, or when it’ll wake up during sleep. This is an ongoing issue and Microsoft says it’s intended behavior which is infuriating. The suggestions in this thread are all good. As much as I hate having to work around my devices instead of working with them, this is the fix that’s had the most dramatic results for me: Laptop Fan Ramping Up in Sleep - #15 by Mr_Darcy