System shutdown / hybernate after 20min running kodi

Hi, so here is my setup a ubuntu 16.04 minimal with Xorg and LightDM on a computer with an Asrock motherboard with a baytrail cpu
and autologin for kodi session

The computer is running well 24/7, but when I start reading a video (whatever it is) or TV then after 15/20min the system just shutdown or hibernate with no reasons
I tryied and search the logs, but there is no kodi crashlog, nothing in system.log or Xsession.log or Lightdm.log appear at the time of the shutdown

So I’m lost with that thing,
Did somebody has the same issue?
Maybe I’m not searching in the right place so any help is welcome
thanks
best regards