Power and Home button unresponsive, screen is black but phone is on

I've had my iPhone 5s since December of 2013, and in this past few months I've had this issue start happening for the first time in the device's history. I will be browsing (whether it be Facebook, YouTube, ect.) and the screen will start to glitch and become unresponsive, and then after a minute or so will turn black. It will still play audio and Siri is responsive using the 'Hey Siri" command, but otherwise the phone is useless. This is the third time it's happened. The only way I've found to get around the problem is to wait for the phone to die completely and recharge it, which takes a lot of time since it can't be used while waiting. Is there another way around this, or am I going to be stuck with a half-broken phone until we can afford a new one? Also, the home button hasn't been working regardless of if this occurring or not. Thank you in advance to anyone able to help or who tries to help me. Luckily I was home this time so I could get to a computer, last time it happened while I was on a bus heading away from home and my bus pass is on the Trimet app on my phone.