Check engine light comes on and off? Wth?
 

So about a week ago, I replaced my spark plugs and wires, cleaned my MAF sensor, and did a fuel injectors cleanup with the additive stuff from autozone (like usual). Ever since then my car has been running MUCH smoother and faster, and sounded like it gained a lot of HP...I haven't changed my plugs in over a year...bad I know, right? Anyways, about 4 days ago, my check engine light came on while in the middle of driving. I started freaking out. The car sounds fine though. The next day, I turn my car on to go to the Mazda dealership, and the check engine light isn't on! I'm like, wth is this? So I went about my business. The next day, it comes on again, this time at start. I started driving to the dealership, and it turns off middrive to the dealership. The check engine light keeps coming on and off. What should I do?