My Galaxy S5 flickers badly in low-light situations, as if the battery or some kind of power thing is going bad. After extensive digging I finally found the cause. I fixed it (August 2017) with the following technique on the phone:

• Go into the Settings by tapping the gear icon:
• Under the small “System” title / select “Developer Options” /
• Under the small “Hardware accelerated rendering” title…
• check the  “Turn off hardware overlays” box

Reasoning: The hardware overlay allots each app a portion of video memory, so that the little computer in the phone doesn’t have to work hard mediating collisions and clipping among images trying to display on the screen.

For some reason the hardware overlay on my Galaxy S5 phone doesn’t work right, causing a serious flicker on the screen that makes it almost unreadable.

So I turn it off after every restart, to keep the display coherent. So far it works well.