The other day I was driving and randomly 2010 civic started shifting rough in lower speeds as well as the RPMs were high. By the time I stopped the check engine light was on and the D light was flashing. It seemed the transmission fluid was low so I topped it up. When I restarted it, the D light was no longer flashing and my ride home was pretty smooth

I took it to my mechanic who took it for a drive end it drove perfectly for him. He tried to read the code but couldn't find one

I took it back and it was good for another 50 km when the rough shifting and high RPMs started again. It seems that every time I turn off the car for a bit it's fine when I start it up for a bit before it starts up again

Does anyone know why this is happening? I have seen other forums where others have the same issue as me and they all say that even honda cant get a code reading or figure out the issue

If anyone has any insight I would be very grateful.