buick lucerne cxl

Hi everyone! I bought a Buick Lucerne CXL '06, for me elderly dad. Everything's been pretty good till recently. He started having issues with the car not shifting and locking up. He would drive somewhere, and when he would park the car, and return shortly thereafter, the car would not come out...

I own a old buick lucerne 2006 all stock parts and recently i have noticed that on hot and verry cold days my transmission likes to randomly start shifting hard but then all of a sudden fix its self. Would this be my ecu actig up of old age or something else? Its not a major problem it just has...