Phone fixed itself

[Cupidloserface]

Yo! So my phone started doing this thing.. When I locked it, or the screen timed out, and I tried unlocking it, it would flash green\yellow and go black. Sometimes after pressing the lock button a few times, it would come back on. Other times, I would have to remove the battery and restart it. I did a factory reset twice, but it still kept doing it. So I downloaded the app "Stay Alive" to keep my screen on. I kept it on for slightly under 2 weeks, when I accidentally locked it and exclaimed "OH NOOOOO!" but it came back on just fine. I didn't trust that it was fixed so I still kept the screen on after that. Then, after a couple more times accidentally locking it and saying "OH NOOOOO!", I realized that it wasn't having the issue anymore, as it came back on just fine each time. Since yesterday, I've used it normally, locking it when not using it. No problems whatsoever. It hasn't been exposed to water. It's technically a water-resistant phone, but since I have trust issues, I've never tested it. It has, however, been dropped a number of times, so I thought that was the issue and that my phone's days were numbered. But now it acts like there never was an issue.. I'm not complaining but I can't help being skeptical. How did it fix itself?

 

[Fox Mulder]

Only your phone knows the real answer and it isn't talking. Just accept the minor "miracle" and cautiously move on, taking care not to drop it any more. It may be ok forever or on borrowed time until the problem returns, there's no way to know.
It's good that you chose not to "test" the IP67 rating, that usually doesn't go well.

 

[PitCarver]

Your phone may just be teasing you.
Mine started doing the same thing, last year. At one point it appeared to have corrected itself, but then it came back. Finally, it stopped coming back on.

Had to replace...

While you've still got it going, make sure to get your backups done. Move everything you can to the MSD card. Back up your contacts, app settings and anything else that you'll need to transfer to a new phone.

 

[Kiriakos_GR]

It's good that you chose not to "test" the IP67 rating, that usually doesn't go well.

Samsung S5 User manual does not say much about tips that any user he is obligated to do as maintenance in favor to proper waterproofing.

1) It does not say … DO NOT remove the back cover with out a good reason. (plastic hooks over the cover goes bad after 50 removals)
2) It does not say … Add baseline over the back cover O-ring every six months.
3) It does not say … Use microfiber cloth to clean from dust and dirt entire surface at the back of the phone before you attach the back cover.
4) It does not say… Get a wireless S-view cover so to remove stress from the charging port.
5) It does not say … Keep your own charging cable in to a dust free environment and away from your food. S5 charging port this is protected from dust and pollution by it own protection cover, but power cables plugs get dirty if you are not careful enough, due such a cable you do transfer dirt at the charging port.


S5 G900 this is safe from water if you do all above, and never replace it screen at unauthorized service center (Original screen shields intact).
Practically, if you do all above and add also one Nillkin H+ tempered class over the screen, the phone becomes strong as fortress and water proof as submarine.
Original S5 back cover it is a poor choice but Samsung did it to keep this phone slim.

Original S-View cover this deliver lots of protection but the wireless charging version it is by far most wise selection.
With all above in mind phone electronics will stay healthy for decades, except if you are using S5 for navigation and this is exposed to enormously high temperatures under the sun in your car.

Problem report at first post could be caused due unreasonable exposure of the screen under direct sun-light.