Hard shifting

[Maxtech]

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 me curious on why it would do this. Also my transmission fluid is fine and doesnt smell burt at all.

 

[2007LucerneCXL]

Look through the Lucerne forum as there may be additional information but here's a recent post on a similar type of problem.
Tiny jump shifting gears
Also depending on mileage a transmission fluid and filter change may be something to consider.