Does anyone have booking.com app installed? After installing this app to check on some reservations I had made on my computer this started happening. Did a bit of searching on the web and found this youtube video showing the same problem. Someone said uninstalling app, clearing safari and rebooting phone worked for him, didn't work for me but its worth a try.
I have had booking.com installed for months, so I doubt there's a relationship. I have not upgraded to 9.3 (I'm on 9.2.1), yet I suddenly developed this problem yesterday morning (March 26). I will try deleting my booking app, but I am guessing I'll have the same results as you.