I have this issue too. My Galaxy S5 has beening doing it for a while. Mine was new in 2014 and otherwise continues to work very well.
Everything appears normal. The device starts properly (from a cold start) but once startup is complete, it's intermittently unresponsive to certain tap and swipe gestures.
This unresponsiveness is most consistently noticeable on right swipes necessary to open into the home screen, from a screen locked state.
I don't need or want to use any of the screen lock security options and keep those options turned off.
I do have 2 fine cracks in the Corning Gorilla Glass from a couple of drops. Could this be effecting it? I'll get a new Gorilla Glass protector and see if this helps.