The DayZ lagging issue on Steam can be caused by different factors. It could be due to a game bug, outdated drivers, corrupted game files, internet connection, or even hardware compatibility issues.
On an unrelated note, DayZ Hotfix 1.7.2.5 has been released for bugtesting. The update's changelog lists fixes to graphical glitches featuring both barbed wire and dead bodies, as well as an issue ...