I found that mine tend to slide about when I change display settings, especially after a safe-mode boot. There are free utilities that will save your icon layout and restore the save file; this is how I do a reset.
Sorry, I'm not at home, so I can't tell you the name of the one I use.
Cyberat_88, different people are comfortable with different styles. Besides, OP did not say s/he had a hundred icons, just that they moved.