Transmission shifts late until warm
I have a 2012 Nissan Versa 1.8s with the 4 spd auto transmission (not cvt). 106,xxx miles. The issue I’m having is when I’m accelerating the rpms will go all the way up to around 5 or 6 then drop down to 3 or 4 and then shifts into the next gear. It only happens until the cars warmed up. Once it is warmed up though it shifts perfectly fine. im not sure if this is something normal or what it may be. I thought I might just need to drain and refill the transmission fluid but I’m a little nervous from all the different opinions on changing out transmission fluid.
Does anyone have any ideas or suggestions?