Find out what causes freezes of my phone
The question is very general but I can give you some common reasons why phones freeze and some troubleshoot steps.


Do a restart by holding the power button and then press restart.
Find out which apps are using the most system resources and unistall them, then check if that fixes the problem. (Common apps like this are Facebook and Facebook Messenger). This app can help you fix RAM issues.
If you see any errors during the crashes post them in the comments or edit the original post
Last option would be to factory reset the phone but as the website says, all described operations you are doing at your own risk.


p.s. also, its not a good idea to post your build number on a public forum.