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In the meantime that is an unusual issue, especially for an S series phone.
When this happens is it, once it starts it's like this for hours, minutes, just that one time?
Does restarting the phone make a difference? Let's say you notice this start and restart the phone does that end it? Have you tried this?
Since you are indicating that this started, ended and has returned, with the first two seeming to be due to updates, have you cleared your partition cache? It used to be with Android updates the norm was to factory reset after an update. It's gotten better since then but bugs still pop-up and they can often be squashed with a partition cache clean up. If you don't know how to do this there are directions online and videos at YouTube.
Since I'm not sure if you can recreate this condition or if it just affects you randomly but another good test would be to see if it happens in Safe Mode. You mentioned that you didn't believe this was being caused by an app, well SM could tell us this if you can reliably say if it does or does not happen in SM. Since SM stops most apps not connected to system apps this is a way to figure out if the issue might be system or app related. App issues should not happen in SM so if it happens then it likely a system problem, if not app problem.
That's really all I have for the moment. Let's know what you find and we'll go from there.
Best wishes.
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