The check engine light can come on for some very slight variation in some signal to the computer. The most common is probably from a momentary misfire, perhaps caused by a spike in the ignition system or fuel delivery that lasts for milliseconds. If it's important enough there will be a code that you can scroll to, but I've had the light without any code showing.
The last time it did it to me was a week or so ago. I'd visited some friends for dinner and they live close to Newcastle beach. The air was totally saturated with salt and the humidity seemed as high as a sauna. The heat was stifling even at about 10pm when I was heading home. The bike spluttered (very unusual) as it started and the light came on. I let it sit and idle for a while until everything stabilised, turned it off and restarted. The light was gone and the bike ran happily. If it's a minor thing the light will go out at the next restart. If there's a code it will generally take four or five restarts for the light to go out.
From Woodrising (no, nobody else has heard of it either) Rides a Springfield Dark Horse