I have a 1999 Mitsubishi Galant V6 with 162K miles. After driving about 30 miles we stopped for lunch and when starting the engine it shook for a few seconds and stopped. I then restarted and it smoothed out so went on the freeway and soon noticed the engine temp was above the "H" so I exited and stopped at a gas station. Added coolant and it quickly went down to half way (normal). So was about to go back home and then for the 1st time through this entire time the Check Engine light came on and remained for the 40 miles back home even though the engine seemed back to normal. Should I disconnect the battery to see if it goes away, now that it's no longer overheating, or should I take it to a mechanic to be safe?