2015 Q40 w~170K miles

Transmission is acting funny, sometimes just clunks while driving especially when cold - and the other day I was driving and I was probably in 5th gear, and I was heading up a hill doing about 60 --- slowly start to decelerate with my foot on the accelerator all the way to the floor. Decelerated to about 50 and then pulled over and shut the car down - when I restarted it the car acted fine. Wondering if this is a transmission control acting up or if it is a main computer issue.

(Some background on the trans - Had a trans issue about 8 months ago and had the valve body and speed sensor replaced. Symptoms - clunk when starting to move when the trans was cold and then at one point I only had 1st through 3rd gears --- when the car was at the mechanic being checked out the other gears magically became available again -- before changing out the valve body and sensor. )

Any thoughts on the issue and potential fixes?