This happens to me too. For whatever reason I got into the habit of dismissing all of them every turn, and I accidentally move troops at least once a game, usually do to a lagspike, as mentioned above. I'm trying to get into the habit of not dismissing them, but it ain't easy to break the habit, especially since not all of them go away at the end of the turn. I recommend making a conscious effort to pay attention to what goes away automatically and what doesn't. For example, I know to manually dismiss war and peace declarations. It's a pain, but I feel like memorizing which ones go away and which ones don't helps me. Or at least makes the tedium of dismissing 15 declarations of war between city states allied with warring civs more mentally stimulating. (Seriously, I get that knowing Gilgabro declared war on Poundmaker is important, but I don't need to know that Akkad declared war on Vatican City, especially since there's an ocean between them.)