For the past few nights my Lenovo desktop (B40-30) has been turning itself on automatically in the middle of the night. At first I thought perhaps the power button was depressed by a book next to the computer. I checked and that wasn’t the case. After searching google I’ve found that this is a common problem experienced in Windows 10.
It turns out my wifi driver was set to automatically turn-on my desktop if prompted by wifi. This problem was solved by turning off the option to allow my desktop to be waked by the wifi network, which was checked.