I've noticed that Riley never sleeps on the turtle basking dock, since at night my central a/c is set to around 75 degrees, but tonight he is for some reason. Might it harm him in any way? There aren't any cold drafts going towards him, but I'm afraid he might get cold. I'm trying to decide whether or not to wake him up and make him go in the water
No harm. Sometimes turtles sleep on their docks. Some turtles do it more than others.
Any time there's a change in behavior, however, be alert for symptoms of illness such as lethargy or loss of appetite. Otherwise, it's just your turtle expressing his/her personality!
Mine do that too, i get a little worried when they rub their head though..Maybe the cold from the AC and the fan is a cause(but its out of my control)since it gets hot overnight in my room.I do cover the top of the tank with a towel.If that helps.