6s plus 10.3.3 ringer turns on and off itself automatically
I have 6s plus 16gb.
It's been 1 week since updated to 10.3.3, ringer has begun to turn itself on and off automatically.
It happens no matter device is locked or not; after unlocking, it begins continuously with every touch on the screen. After that it happens once a minute.
It also gives a vibration feedback so that's how i know it happens while phone is locked.
How can i solve this problem?
iPhone 6s Plus, iOS 10.3.3, 2gb left on storage