Why does the Restart Instruction keep popping up?

Recently my phone has had the Restart Instruction , "To restart your phone, press and hold power and volume up buttons for 10 seconds" popping up all the time without me even trying to restart my phone. I try to take it off by hitting the screen on/off button and it goes away after a few click, but it ends up coming back. I'm still able to use my phone but the message is right in the middle of the screen so it makes it hard to see what i'm typing. When I hit the home button while the message is still on, it'll take a screenshot. Also sometimes when the message goes away and it looks all clear, I hit the home button and it still takes a screenshot. Like if the message was still there just invisable. It's been happening for a while and it's gotten very annoying and frustrating