Shake in the steering wheel on Toyota Prius Classic?

Alignment - you may have hit a pothole and thrown one of your wheels out of line. If the effect is THAT radical, you may have busted a stabilizer bar, or your ball-joint is about to go. They're easy enough to check yourself. For the stabilizer...turn the wheel away from the car as far as it'll go. Bend down and look up the wheel-well. You can grasp at the stab-bars and give'em a shake. They shouldn't be loose at all. Ditto for the ball-joint. If you feel/hear movement or knocking, get them fixed TOP SPEED! You don't want one going while you're driving quickly...they'll send your car in a random direction. Walls, cars, trees, people...ya never know who or what you'll hit.

Sounds like your tracking needs attention.

you need to get a full steering geometry check

I don't know much about cars but as a truck driver - I have experienced similar problems. My gaffa told me it was the tyres needed balancing and eventually I nearly had an accident as the truck pulled to the left on braking. After refusing to drive - the truck was sent in for repair where it was found to have a cracked and worn bearing. If the steering rack isn't installed correctly and has been hurried - this can give similar effects. I would not drive until it has been repaired as you may not just cause further damage to your own vehicle but someone elses also. suspension is also something to check- if you have unbalanced suspension it can create problems. Sorry if this doesn't help but PLEASE - if not for your vehicles sake- then for your own and others safety DON'T drive it until the problem is resolved- PLEASE!

Hi,I would take the car to a good tire dealer that you approve of.They should be able to put the car on blocks and run it up there to check for different conditions.This will eliminate a lot of trouble shooting of the causes you have been put through on the road.Good Luck.

Check the bearings and tracking and steering fluid

check tire pressure in all wheels. Balance them again because if they did it right you wouldn't be getting this vibration. IF they did balance correctly and you still get this vibration, then you MUST have uneven tire wear, meaning one tire or more are worm out more or less then the others. Alignment won't hurt either, but definitly check for tire wear.