I do use Good lock and multi window but I have disabled all that and ran the phone in safe mode and the lagging is still there.
May be hardware? But I am not sure. I have no explanation since you did a factory reset and my s10 does not experience that.
But I do not want to advise you to bring it to a repair shop for a phone that is probably fine and maybe has no hardware issues.
I do not know what to say this time around