[AC Question]

I am worrying for my LG G4. The problem arose today, on Facebook. In the middle of typing, the system froze (couldn't even turn the screen on and off), then it went to black. The LG screen would show, and then go to black again. For the first two crashes out of the three, it would go back and forth before moving on to the Verizon screen.
The third crash wasn't as bad; the LG screen only showed up once before moving on to the Verizon screen.
My phone has a Samsung microSD installed, as well as a third-party ZeroLemon battery. I am wondering if either of those, or a problem with an app, is the cause behind these crashes.
What are the steps that can be taken to address this issue?