Why would my car lock while running and not let me unlock it

If the tumbler on the door is not working, that's a separate concern you must resolve with the keyed lock cylinder. As far as why it locks - typically vehicle doors will lock in accordance with settings that are in place for safety. You can choose to turn this on or off. However, why it will not let you unlock the doors -- not sure. Could be some kind of electrical system concern, body module concern or low battery voltage concern. Hands on testing is needed. www.repairpal.com/repair-shops