I don't know if this should belong in the iPhone forum or the iOS forum, but I am experiencing it on my iPhone 6. When I open Siri it will act as if it's listening to me but the screen shows that it hasn't started yet, and it doesn't listen. I have to go in and out of Siri a couple of times then it works. I don't know if it's a bug or a problem with my specific phone. Anyone else experience this?