iPhone becomes unresponsive when notifications are clicked on

For the past two months my iPhone 6 Plus 16gb has occasionally been crashing and becoming unresponsive. It first happened when I swiped down the notification centre and clicked on a message and it just disappeared rather than taking me to messages. I tried again with another message and again it disappeared so I tried clicking the home button to get to messages that way but the home button had become unresponsive. The touch screen still worked perfectly fine but I had to stay on whatever app I was currently on because of the home button not working. Then I thought maybe I just needed to lock my phone, leave it for a couple seconds then unlock it again but then the lock button stopped working as well and my phone wouldn't turn on. I ended up having to do a hard reset and every time this happens (two or three times a week) I have to do a hard reset to get it to turn back on again.

I'm not really sure what's wrong with it because the rest of the time it works fine and all the buttons work, it's just when I go to click a message in the notification centre that it stops working.

Has this happened to anyone else? Any suggestions of what I should do?