My theory has always been if the check engine light is not going to behave consistently I'm not going to worry about. These things do have random hiccups now and then that are not repeated. You might pull the codes to see if there is anything there but I wouldn't worry about it until it comes back and stays on. Could be somehow related to the idle issue but doesn't seem likely given that they don't occur in sync. I'd be more worried about attacking the idle issue if I were you.