2001 honda civic check engine light goes on then turns off?

I have a 2001 honda civic with high mileage. I just took it on for an oil change and put summer tires back on. A few days later the check engine light came on and then shut off and then came back on and goes on and off every few days. The car doesn't seem to be driving bad although it does seem to shake a little bit. What could this be?

That means there's an intermittent problem… Sometimes it is working properly… Sometimes it is not. The trouble should be stored in the cars computer… You will need a scanner to retrieve it or next time it is on stop at an autoparts store and they will retrieve the code for you for free and tell you what the problem is