Me too, on two different iPhones. Was working fine up to the other day then sticks after a couple of seconds. Once it popped up a window on the scene to put the phone in Google Cardboard; most of the time it doesn't get that far. Mobile Safari ends up crashing after a minute or two after being stuck. However, in iOS Chrome on the same phone, everything works fine.
Mobile Safari info:Mozilla/5.0 (iPhone; CPU iPhone OS 10_2_1 like Mac OS X) AppleWebKit/602.4.6 (KHTML, like Gecko) Version/10.0 Mobile/14D27 Safari/602.1
iOS Chrome info: Mozilla/5.0 (iPhone; CPU iPhone OS 10_2_1 like Mac OS X) AppleWebKit/602.1.50 (KHTML, like Gecko) CriOS/56.0.2924.79 Mobile/14D27 Safari/602.1