My note 4 (N910C EXYNOS variant) has been working great for a year (bought it when the note 5 came out).
But between late 2016 and early 2017, my Note 4 started to overheat, freeze and started to boot loop.
The only way I could stop that boot loop was by putting the phone in a ziplock bag and placeing it in the freezer for it to cool down, and then turn it on while on the freezer.
I’ve tried almost every lollipop, marshmallow and nougat rom available. But this problem wasn’t fixed by installing roms. I used the NEMESIS REFINED ROM, it worked great, awesome. But still, I couldn’t use gps, lte, max brightness, Spotify and google maps while I was on the street, without the phone restarting and becoming useless.
I used every touchwiz based rom and the problem still wasn’t fixed.
I tried AOSP roms instead, I used the bliss rom based on stock marshmallow, but had huge bugs.
I used lineage os and resurrection remix roms based on nougat. They worked great, but I missed the s pen features and also, the problem was still there.
The only way I’ve found to get the phone not to reboot as much (as much, not definitely), is by having as few installed apps as possible. And installing the famous note 4 fix, wake lock, and enabling parcial wake lock and auto start.
I haven’t tried (and probably failing) to downgrade to kit kat because I’ll loose to many features like google assistant (I use it a lot) or the new s pen features.
Currently, I’m using stock marshmallow, non rooted, with wakelock installed, it works better than I expected, the phone overheats from time to time. But it rebooted only once in the whole week I had it running stock MM.
This is a hardware issue caused by a software update, no doubt about that.
The only thing you we can do is, installing wakelock, having as few apps as we can, and start saving for a new phone, because it will not hold on much more time...