Why does watch vibrate for no reason?

I keep getting phantom vibrations, I look at the screen and there's no notification, nothing, I just see the clock. What is causing the watch to vibrate when I'm sitting and doing nothing? And no it's not the move alert because I turned that off.  I have so many issues with this watch it's not even funny. I'm considering going back to the Vivosmart 4 watch,  but I like the look of this one.