Galaxy S4 weird power on/off problem

[stabbymcpeppers]

About a month ago i was in my backyard when my lg bt headset alerted me that my phone was out of range. I took the phone out of my pocket, tried to turn it on but nothing happened, black screen. I tried plugging it into the wall, no response. I did battery pulls, button presses, checked with a known working battery...nothing (just a black screen, no signs of life whatsoever)!
At the end of the day I decided to just pull the battery and figure out what to do with it later. A couple weeks passed and I popped the battery back in, pressed the power button and the phone came to life. I left it alone for a while and then powered it off and it would not turn back on (same as before, no life). I again left it alone until about 3 days ago, put the battery back in, pressed and held the power button and the phone came to life.
I did a complete wipe/factory reset of the phone a couple days ago and it was fine. I restarted it yesterday and it was ok, then I went through the shut down process again just to test a fresh phone and it still has not turned back on.
I tried after 1 hour, no sign of life. I tried after 5 hours, no sign of life. I tried again 24 hours later, no sign of life. Judging by the previous time, it takes maybe 2 days for the phone to be able to turn back on after being without battery.

I have none of the clues. None of them. I appreciate any advice/input.

TMO GS4 on KitKat 4.4.4, about 1.5yrs old.
Always stock, never rooted.
Always in a case, never touched by water.
OEM Samsung chargers only.

 

[belodion]

Welcome to AC.

Possibly, a faulty power switch? Or a poor battery connection?

Posted via the Android Central App

 

[stabbymcpeppers]

Thanks for the welcome.
If it were the power switch, wouldn't there be problems using that button at other times as well? No matter how many times I try to press it, the phone will not respond once it has been shut down. Then one day it will just allow itself to turn on with one press and hold of the power button. However, while the phone is working, the power button will turn on and off the screen every single time without a hiccup.
Battery connection doesn't seem likely since this problem only occurs if the phone is shut down. Last time it was working I was being a little rough with the phone and it never even flinched.