Why does my computer wake up after a couple minutes of going to sleep?

Okay I know the simple keystroke or movement of the mouse will make it wake up but I dont touch the mouse or the keyboard neither does my cat or dogs, it just turns on at random, I downloaded something and it may of been a R.A.T. but I scanned my computer with malware bytes and AVG and it didnt show up. but other things did so I got rid of them, why does it wake up at random?