There are so many different reasons for the check engine light to come on, that it will be impossible to even start to guess until you have the codes read. I doubt the spark plugs are the problem. You need to have the codes read, reset and go from there. Stray codes are not uncommon and do not necessarily indicate a problem unless they reoccur once they have been reset.

I purchased a code reader several years ago just to avoid the situation you describe. I can check the codes when they come up (and they do come up frequently) and reset them. If the code returns, then I know I have something that needs to be addressed and I have a pretty good idea what the problem may be.