I just had my front left bearing replaced on my 98 Outback, but on the drive from the shop, I noticed that my car seemed to shake, sometimes very violently, while I drove. It was a little random with how fast I was going and when it shook. Not sure if this is normal, or if I should take it back and get it checked out again

Definitely get it checked out, sounds like something got left loose.

well you are very right you should go to work shop and get it check out again.