Why is my ringer changing from silent to alert by itself?

[iMore Question]

I have an iPhone 5, recently upgraded to iOS 9.2. The phone will randomly buzz, showing the volume box with bell with the volume adjusting, then showing it in silent mode. It will do this 5 or 6 times, then behave for a day or so before doing it again. Is this an issue with the OS upgrade? It did not do this on the previous OS.

 

[Just_Me_D]

I don't know because I'm not experiencing anything like that, but I'm not using an iPhone 5. I'm using an iPhone 6 Plus and 6S Plus.