Shut off while driving and wont start

i have 1995 toyota LE 4cyl 2.2 with `16800 miles
tonight when i shut off engine with key out motor just keeps running. i had to to take cable off battery to stop it. what would cause this? i need your help! please! thank you! michael

The problem you're having is dieseling/run-on is being caused by an open throttle plate clean out the throttle body/plate re-adjust the idle speed and check the throttle position sensor. An engine overheating can cause this problem too.