Slipping gears, overdrive button flashes

What is your question?

I started my car and put it in gear but it did not move, with the gas pedal lightly pressed, but I put it back in park, then reverse and back to park then in to drive, it was fine afterwards. Today while I was driving it made the rpms rise and jumped or skipped over a gear before dropping the rpms back down. At the same time the overdrive light was flashing then it stayed illuminated to which I had to manually press the button for it to go back off. What does that mean

What makes this problem better or worse?

Driving long distances ( like 20 or more minutes between starting and shutting off vehicle)

How long has your 2000 Nissan Maxima had this problem?

Started today