Re: Why does my Samsung Galaxy s5 keep turning off and on by itself
Two possibilities come to mind. Look in the battery in Settings after it turns on the next time. Tap the graph at the top to get to the next page.
Look for a "fall off the cliff" - IOW, a drop in just about zero time to just about zero voltage, then the voltage is back where it was, or a little lower. If you see that, it's a bad battery. Lithium batteries grow things called dendrites (search
lithium battery dendrite and you'll learn more than you want to know about them). They're basically crystals growing across the battery, shorting it out. The short draws enough current to cause the phone to restart or even turn off, and also blows the crystal like a fuse, leaving you wondering what happened. You can try to convince the carrier to replace the battery under warranty (it's certainly a "manufacturing defect" - it's a decision in design defect to use lithium batteries, knowing that a certain small percentage will fail this way - even though there's no decent option at the moment unless you want to carry a 5 pound lead-acid battery around), but most of the time you won't get far trying that, even if you print up a few web pages showing that it's a known fault.
The good news is that a good quality replacement S5 battery is only $12 (plus shipping unless you need some other stuff - I order cat litterbox supplies at the same time I order anything else - that alone is over the free shipping point). See
http://www.amazon.com/2800mAh-Batte...ag=hawk-future-20&ascsubtag=UUacUvbUpU4252613 for the battery.
The other possibility is an intermittent power switch. If you hold the power switch in long enough, the phone will restart. (It's a kinda-sorta battery pull - it doesn't reset hardware, like a real battery pull and power switch press does, but it fully reboots the phone.) If that's happening, the phone is under warranty - back up
EVERYTHING you don't want to lose, and bring the phone in for a repair or replace.