New
#11
Having just seen this thread, I'm also necroposting just to say that the Start menu pops up upon waking from Sleep if you used the Start menu to put it to Sleep in the first place. The reason for this is that Windows always wakes to the exact same state it was in before sleeping, so in such a situation that "previous state" was one which had the Start menu open (because you opened it to put it to Sleep).
I don't think this was the behaviour in previous versions of Windows. One would have assumed that the mere clicking on Sleep would be enough to officially close the Start menu.
Several users have already submitted this issue on the Windows Feedback app.