Q: Reduce engine power / check engine light is on

Left the car on to run into the store and when I came out I noticed the exhaust sounded different; it had a putt/putt sound to it; when I got in I noticed the check engine light was on along with a reduce engine power message; it was drivable however ran a bit sluggish - when I turned it back on, the reduce engine power message was gone, however the check engine light remained on. I was able to drive it without any additional problems, but when I came to a stop the reduce engine power message appeared, and stayed on for a while but then went off again. I've noticed that the power windows take a while to roll up, and if the interior lights are on, and I lock or unlock the door they tend to dim. Not sure if the problem is related, to the reduce engine power message - however the message remains off & currently only the check engine light is displayed. Planning to take it in to run diagnostics on it tomorrow, and hoping it's nothing major. Any thoughts/ advice?

My car has 113000 miles. Update: This morning the check engine light was off, and has remained off thus far.

It came back on and has remained on.