Check engine light intermittent on/off

[Gort400]

Scenerio: Owned car for almost 14 years. Check engine light has never come on. 3 hour interstate drive last night, All fluids checked prior to trip. Full tank of gas with Carb/fuel injector cleaner added to tank. 2.5 hours into trim I noticed the check engine light came on. Car performing great. Fuel consumption normal. Temp normal. No abnormal noises. Check engine light went off after @10min. This happened 2 more times. The light was off when I arrived at my destination. Stopped at traffic light prior to hotel arrival and the idle engine RPM was normal. Waited to check fluids in AM. All fluids checked normal this morning. Nothing seems out of place in engine compartment.
Questions: Will a code still be posted in the computer? I don't have a code reader. Are the big box stores code readers reliable? (ie Autozone, Advance Auto,or O'Rileys) Has this happened to anyone before. Thanks in advance for any ideas. Joe

[goody90q45]

Codes will still be stored in the ECU. Auto parts store will only be able to read codes if your Q is 96+. For 90-95 you'll need to pull the ECU and count flashes on the back side

[Gort400]

Mine is a 1995 Q45. Sorry I forgot to mention. Where is the ECU? Is it easy to pull? Any cautions. Thanks