My computer is turning on by itself?

I'm running Windows 10 on a Lenovo computer: 1TB HDD, 12GB, AMD A10.
At first, I was putting my computer in sleep mode when I wasn't using it. I noticed that every now and then the screen would turn on. I assumed every time that something had slightly moved the mouse (dryer shaking the floor from next room, someone walking by the desk, etc), so I chose to shut it down. The computer is on a desk that sits right underneath my TV, so while watching the screen, I can easily notice the computer do something. About a half an hour, maybe a bit more, went by after I had shut it down and I watched as the computer powered itself back on.
Is this some kind of virus, motherboard issue, or common thing with Lenovo desktops? I'm seriously freaked out (though I know there's got to be some kind of explanation) and I've resorted to unplugging the tower after I shut it down, which is a hassle because of the location of the desk.