Was your computer sleeping or actually fully turned off, when it would power on by itself? Seeing as we're talking only about a software difference (10 vs 8.x), it seems improbable still to be the...

Your GbE adapter isn't Wifi. Unless you're plugged into a LAN, and sleeping the system, it probably isn't that. However, you could have something in your system BIOS that is triggering the boot. ...

Maybe you have some wake on WLAN function enabled or something and there is something triggering it.