Why does watching videos on chrome turn off my phone?

[AC Question]

Basically what happens is whenever I watch a video online on chrome my phone screen turns off and on again. And as soon as I unlock my phone and press play it crashes again. I don't know what causes this, my phone is an android Alcatel idol 3.

 

[vincezeboss]

Currently i have exactly the same problem ( on idol 3 5.5"). I can watch videos on Youtube, but when im in chrome, videos crash, then screen turns off, wallpaper changes for the defaut one, and then the phone turns on again...
This problem came like 3 weeks ago... And i don't know what to do