iPhone x isn't going to sleep

Help! I've searched and searched and I'm not finding any sort of solution. I've restarted, I've reset. My iPhone X doesn't always go to sleep on it's own. I've ensured it's set to timeout after 30 seconds. There are times when I unlock my phone and it doesn't go to sleep. Or when I receive a notification, it doesn't go back to sleep. VERY FRUSTRATING! It's KILLING my battery life!!

Has anyone come up with a solution??