Samsung S4 Android 5.01. Powers off at overnight when fully chargedm why?

[AC Question]

Samsung S4 Android 5.01. Powers off at overnight when fully charged

It started a week ago. I plug the charger during night and at some time during bed time I see the phone has turned off and the battery full on the display.

I thought it was something occasional, however its constant. If I leave the phone running on battery nothing happens.

Is there a way I could check log events at android level to see if something is triggering the power off?

any other suggestion?

GT-I9500
kernel 3.4.5-4967951

Thanks