I just purchased 2004 awd Murano with 140000 Miles.
I was going the freeway about 65mph and my rpm was as high as 4. But driving didn’t seem like it was going through 4rpm, rather regular. It was fluctuating widely. I stopped the car turned off and on again and continued my way, after I restarted vehicle my rpm was about normal and almost not fluctuating at all.
There is no check engine light.
What would this be? How can I avoid this? Thank you

The engine and transmission in a Murano are controlled by a computer. Occasionally, computers have glitches which are readily resolved by a reboot. However, I suggest you have a code reading done. I have found new codes, even though the check engine light was not on.