Why does the check engine light stay on then flashes for seven or more times? on 1997 Lexus ES300

When I bought the car few months ago the car had a bad shake to it when you was going 50 miles and got better the higher speed. Come to find out from hooking it up to a computer it was a misfire. Changed the spark plugs( they had the wrong ones in) and the oil. Now it seems to doing a different shake.

Asked by for the 1997 Lexus ES300