Brief acceleration issue

[salmonz]

I have a 2007 Toyota Yaris with 64000 miles.

Today when I was accelerating after sitting at a traffic light, I noticed my Yaris did not accelerate, rather it revved to about 4000/5000K RPM, and shuddered.

Sequence of events:
It was 95F outside when it occurred.
1. Spent 40 minutes driving 70mph on the highway.
2. Spent 5 minutes driving 35mph in the city.
3. Came to a red traffic light, braked, came to a stop to 45 seconds.
4. Placed my foot on the accelerator.
5. Car moved maybe 3-5ft, then engine started to rev to 4000/5000K RPM.
6. Car did not move, and shuddered.
7. I took my foot off the accelerator to let it go down to 0RPM, then tried again, and the car started to move.
8. I drove for maybe 1000 ft and it started again, however it was different than the first time. I pressed the accelerator, it revved a bit, and 5 seconds later it started to accelerate, but with a shudder.
9. I pulled off to a side street, let the car sit for 3-4 minutes. Continued driving and it was OK for the rest of the day.


What happened and should I be concerned that my engine or transmission is f'd up?