Q: Iphone 6 freezing up

Hi Stereo1370,

I'm sorry to hear you are having these issues with your iPhone. If you are intermittently but repeatedly experiencing freezes on your iPhone when trying to access a built-in app like Messages, you may want to make sure you have a current backup of your data, then try reinstalling a fresh copy of the operating system as outlined in the following article (the article is aimed at a slightly different issue, but the steps included are useful for other issues as well):

If your device turns on but gets stuck during start up

You might see the Apple logo or a red or blue screen for a long time during start up. Try these steps:

1. Connect your device to a computer and open iTunes. If you don't have a computer, you can borrow one, or go to an Apple Retail Store or Apple Authorized Service Provider for help. 
2. While your device is connected, force it to restart. Press and hold the Sleep/Wake and Home buttons at the same time. Don't release when you see the Apple logo. Keep holding until you see the Recovery mode screen.
   
3. When you get the option to restore or update, choose Update. iTunes will try to reinstall iOS without erasing your data.
   

iTunes will download the software for your device. If it takes more than 15 minutes, your device will exit recovery mode and you'll need to repeat steps 2 and 3 again.

If your iPhone, iPad, or iPod touch doesn't respond or doesn't turn on - Apple Support

Regards