Q: iphone6 will only respond to a hard start after being idle for 2 minutes

Yesterday I was running pandora and navigation though maps. When I came to the area I was familer with I turned off maps, a few seconds later my screen was black and the buttons were unresponsive. At first I thought the battery had died so i charged it when I got home. I had to hard start the phone to turn it on and now if it is idle for longer than two minutes it shuts down and will only respond to a hard start. Iphone 6 OS 8.3