I just got a 99 Volvo from my mom. She has never had this problem. It has about 120,000 miles on it. The only thing I have done differently is drive about 600 miles in oneweekend and I filled it with regular unleaded (my mom usually uses 89 grade or 91). Occasionally, when I start it, the car will shake and then never go above 10mph. The rpms doesn't go above 1 either, no matter how hard I push on the gas pedal. If I shut the car off and start again, it sometimes returns to normal. Other times I need to restart quite a few times but once it stops shaking at start up, it runs perfectly.
Could it be the gas I put in? Any other thoughts?
Oh, and the transmission was replaced last year.
Thanks for any thoughts.

 

Stop by your local Volvo Dealer and see if Recall 155 has been performed.
The recall 155 is for the electronic throttle system.

 

I have the same problem with my S80, it happens alot in the morning when i start the car to go to work, it will shake, then i turn it off, count to 30, turn it on and its good., still makes me nervous as hell... but i should probably stop by the Volvo dealership and see if that recall has been performed, thanks for the tip!