[He's not weird, he's dangerous. He's casually violent and purposefully distant, and the fact that's let his guard down so much is starting to bother him. He's yearning for a way to sharpen his edge, all while being afraid of what he would have to lose to do it. He doesn't want to hurt Sheryl. He doesn't want to scare her.]

[And that alone indicates something's wrong with him]

Sorry, it's just a bad habit I have. Can't seem to shake it. I didn't mean to startle you so much. When class starts, please don't go easy on me.

[Hopefully, working hard will help ease the tension settling in his body]