door chime beeps after door still closed

Just wondering if anyone has had this problem. If I leave the key in the ignition and shut the doors the chime still beeps for 20 - 30 seconds with the lights still on unless I shake the key in the ignition or turn the key on. This just started happening today, and I was wondering if the door shut off switch (which I can't seem to find) was stuck or the ignition has problems.

Thanks in advance.