Note 4 restarts, severe lags too

[NicoleJS]

My Note 4 occasionally restarts, but worse there can be input freezes of a minute or more. These lags come in flurries, sometimes not occuring for several hours. If a freeze does not resolve by itself in several minutes, a reboot may be necessary. I sometimes get a "process system not responding" notification. Perhaps unrelated, I get full screen popup ads recently.
I have cleared the system cache, and installed a new battery. I do not want to do a system reset.
Any ideas? Help much appreciated. Thanks.

 

[GameTheory]

I get full screen popup ads recently.

I do not want to do a system reset.

Sounds like you may have some rogue app/s running ads on your device. You should start by removing any questionable apps you may have installed. Many games come loaded with ads.

If it was me, I'd do a factory reset and start fresh. By the way, I also have a Note 4, but runs well. However, I don't have much apps installed as it's not my main phone.

 

[svim]

Try running your phone in its Safe Mode and see if it's running more reliably that way.
https://www.hardreset.info/devices/samsung/samsung-n910f-galaxy-note-4/safe-mode/
Just keep in mind that while running in Safe Mode it's loading just the base Android operating system, that excludes all of the third-party apps/services that usually get pre-loaded into RAM during start up so while your phone should be more stable it will take longer to start up some apps and things as you're starting them up from scratch.

Typically a Factory Reset should be relied upon only when your other options haven't worked out but given the age of your Note 4 it really is something you might want to consider doing. Install Samsung's 'Smart Switch' utility on a computer and then do a full backup of your phone. Don't rush anything and follow through all the directions -- it's important to have a backup solution set up all the time anyway, even if you're not going to do something like a Factory Reset.
https://www.samsung.com/us/support/owners/app/smart-switch
Smart Switch will allow you to do the Restore process too, putting your data back after the Reset. Yes a Factory Reset can be something of a real hassle but if you have a more or less automated backup/restore solution set up than it's a least a viable option to consider.

If your phone is running OK while in Safe Mode, that's an indicator the Android OS is probably OK and there's some issue that would probably be addressed by doing a Factory Reset. If your Note 4 is still running badly in Safe Mode however, than it might involve reinstalling the OS. With smartphones that's referred to as flashing a stock ROM. You 'might' be able to repair your phone using Smart Switch, but that's going to be a pretty conditional thing. If it works that's of course good but if can't do anything than you'll need to do the process manually. Go here to download the appropriate Samsung stock ROM:
https://updato.com/firmware-archive-select-model?exact=1&q=GALAXY Note 4
Be sure to pick the ROM that exactly matches your Note 4 model I.D. (i.e. SM-N910x) and your carrier. ROMs are very model specific so don't mix and match, it's important to flash just the one that's been made for your specific model. For a detailed explanation on how to do this:
https://updato.com/how-to/how-to-install-an-official-samsung-stock-firmware-using-odin