95 Century-Engine Won't Shut Off

I have a 1995 Buick Century with about 92,000 miles on it. Two nights ago I was running errands when this happened... I put the car in park, turned the ignition to the off position, pulled out the keys and noticed that my engine was still running. I put the keys back in turned the ignition to the on position, then turned it off again, and the engine still continued to run. I had a quick stop to make, so I went inside, and came back out about five minutes later to see that my engine was still running, even though the ignition was off and the keys were in my hand. Since then, this problem has happened both mornings when I go to work. Once I put the car back in gear and drive to another parking spot, the engine usually turns off like it normally should. When I turn the ignition off, the radio and fans turn off like normal, it's just the engine that keeps running. The service engine soon light comes on when the ignition is off but the engine is still running, but it goes out when the car is being driven. If anyone has any ideas as to why this is happening, your help would be greatly appreciated. Thanks in advance for your help!!

Sounds like the ignition switch is not recognizing that the engine is shut off. This means that there may be a short inside the ignition switch. If there is, the engine could randomly start or shut off during driving.

Ignition switches are pains to replace. You have to have the labor done, including disabling the SIR, and then you'll need all new keys if they arent able to fix it.

I've been searching through the forum, trying to come across anything that might help me. It's pretty funny to see all of these posts about buicks that won't start, and make it to one where the thing won't shut off!