Lose Power Steering problems of the 2006 Mini Cooper

I was pulling out of a parking spot at a low speed this morning when I lost the power steering in my 2006 Mini Cooper. The steering wheel was very rigid and it was hard to turn. I tried turning my vehicle off and off again. I also tried turning the steering wheel to loosen it up. Nothing helped the issue. I continued driving for another 30 minutes. At a low speed making sharp turns was very hard, if nearly impossible to stay in my lane. If someone would have been in the other lane I would have been in an accident because I could not make the turn due to the lack of power steering with my vehicle. The steering wheel was very hard to turn all the way. Even at higher speeds (30 to 40 mph) the steering wheel was hard to turn and make it around curves in the road. Starting from a dead stop it was very hard to turn the steering wheel turning left or right. I could barely park my vehicle in the parking spot in the parking lot because the steering wheel was so hard to turn my vehicle at such a low speed. This is the third time the issue has occurred in my vehicle during this month. But the other times the issue has gone away after restarting the vehicle twice. One time was two days ago in the morning. I was pulling out of a parking spot and the steering wheel was tight and hard to turn. The other time was over a week ago and the vehicle was this time restarting the vehicle did not fix the issue.