Hi There, so i have a 2006 US 350Z roadster (automatic).
this past year i've been experiencing any issue with what to me looks like the ECU of the car. sometimes the car gets stuck in 3rd and will keep over revving. even if i drop it in TIP and try to physically change the gear to a higher one it does not allow me (sometimes). this usually tends to happen if i am driving on the highway. (so it's a bit concerning). what i do to resolve the issue is drop the car in neutral, turn the car off while rolling and start it again, this usually resets everything and some instances resolves the issue. does anyone know whats going on? and what do i need to do to resolve this issue? is it the transmission? it's getting really annoying and also very dangerous if im doing this on the highway.(Please note once again this is an automatic 350Z roadster 2006)

Please Help!

Your responses will be greatly appreciated.

Cheers!