My RPMs go up and down?

Hello,

You could have an issue with the transmission shuddering. A transmission will shudder when it has difficult time going into a gear. Most of the time the shudder will happen in high gears just like you are experiencing.
Typically most shuddering happens due to low transmission fluid or having dirty/contaminated fluid.
First check the fluid, make sure it is at the correct level.
To check the fluid level, start the car and wait for it to reach operating temperature.
Turn off the engine then check the fluid level.

If the fluid is dirty, you might wan to do a transmission service.

Here is a helpful article:

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

I have attached the fluid check as well as fluid change procedures for your reference.

Please let me know of any questions.
Thank you.