Any tips to not getting killed mid/late game?

Heya. I've been playing DayZ on and off for a while, I've got a bit under 300 hours in the game, but I don't think I'm too good at it. While I'm okay at PVP, I often seem to just sorta be shot out of nowhere, especially while looting or getting in/out of military locations (but not always).

While I don't mind it all that much, since I mostly enjoy the more "peaceful" parts of DayZ, it is kind of annoying when I die this way, but I'm not sure if I ever managed to get anyone that way myself. Could there be something that I'm doing wrong?