Did you select set up as a new phone or restore from a backup I had all kinds of problems like this until i just bit the bullet and did it clean slate, and i h

Did you select set up as a new phone or restore from a backup I had all kinds of problems like this until i just bit the bullet and did it clean slate, and i haven't had a single performance issue since. Not a single reboot, nothing. The regular iOS11 gripes are still there but nothing truly awful like this It's a bit like doing a clean install when you order a new laptop right after you take it out of the box. It's usually a good call, even if it's a bit of a hassle