iPhone 7 Frozen

I got my iPhone stuck somehow today, it wouldn’t respond to touches and then wouldn’t turn off/sleep.
When I held the power/sleep button down for a few seconds (10?) it displayed a “loading circle” and sat there.
I then discovered that if you that to force restart the iPhone 7, you have to press the volume down and the sleep button.
I did that and it restarted and all was good.