I posted this same issue with my iPhone 6 but haven't heard back from anyone about it..
Sometimes when I try to wake my phone, it stays black for about 10 seconds, then gives me the spinning wheel (loading) for a few seconds before letting me unlock the phone.
Other times, after 10 seconds of black and 10 seconds of spinning wheel and finally getting to the lock screen, when I press the home button again, it gives me the spinning wheel again and then back to the lock screen.
Also, if the phone is 'asleep' (black screen) while I am listening to Music, a Podcast, or using my GPS and then I try to wake the phone, the Music/Podcast/Map stops and when I finally get back into my phone, I have to go back into the App I was using and choose a Song/Podcast/destination again to resume listening or receiving directions...
Everything worked great prior to 'updating' - now basic functions are hit or miss and my device seems unreliable at best.