Power steering problem? - 2004 Mini Cooper

I was driving my car home from the store today and it all of a sudden got really hard to turn the steering wheel. I was able to get it home and I tried to check the power steering fluid. Unfortunately, I don’t know where to look after I pop the hood and my owner’s manual didn’t mention anything about power steering in general, much less where to go to check the fluid. So I decided to take the car in to the shop. When I started driving again, the steering was fine. It felt just like it normally does. I drove around for a little while to see if the problem would come back, but it never did. Should I still take the car to the shop? Any ideas why this might have happened?