I'm not sure if this is where we're posting such things, but I figure since my SP3 is still a part of Windows Insiders, I'll go ahead and post here. Strangest thing happened this morning, first time in forever (since many builds ago): I was sitting at my desktop with the system fans and my floor fan running, and heard this really high-pitched fan noise that I couldn't place. Then I realized it's my SP3 sitting there, supposedly asleep/hibernated since last night, with the fans spinning like crazy.
Nothing in Task Manager accounting for it (CPU at around 2%), just the fans going like they have nothing better to do. Weird, and I hope it's not a harbinger of some problem.