check to see if you have downloaded any recent apps that may conflict with or could cause trouble... I'm having the same trouble, when i press my power button on my note 4 to wake my phone , nothing happens, i have to press it like 5 times... it just started happening and i hadn't dropped , damaged, no water , nothing, i started uninstalling apps one by one in reverse order and it turned out to be a generic galaxy note 3 lock screen i downloaded for my note 4 that started causing the issues... best of luck.