Why does my LG G3 Keep rebooting over and over?

[AC Question]

I bought my LG G3 from T-Mobile. Since my purchase I traded in the phone at least 4+ times in the last 7 months because it keeps randomly rebooting until it loops. Ex. turns on then off, then on again and off again over and over. In the last 30 days I traded the phone in 2 twice. Every phone I trade in has the same problem. Like the reboots just transfers from one phone to the next one like a virus. I did a factory reset numerous times to the point where I do not install any apps or upload any google accounts. It still does it. What is this virus that follows me from one phone to the next. Please help me fix this phone glitch. It is very frustrating and am out of a phone because of this.