I backed out of a parking space in a parking lot and turned the steering wheel left then as I put vehicle into "drive" my steering seemed to lock up and became extremely hard to turn. I kept attempting to turn wheel and suddenly it was easily turned again as normal. While I was driving home the power steering stopped working causing steering wheel to feel as if locked again and almost impossible to turn in any direction. I almost wrecked my vehicle and hit another vehicle on the road way but hit my brakes and continued to aggressively turn the wheel to missed the vehicle in front of me. I heard and felt a pop and then steering wheel was easily turned again. I barely missed the vehicle in front of me but I did hit the curb and a bicycle a pedestrian was holding next to him on sidewalk. He was able to jump out of the way and was fortunately unharmed. I stopped my vehicle and parked immediately. I called my husband and he came to get the vehicle and I drove his home. He had no problems driving vehicle home and power steering was working as normal but once he was close to pulling into the driveway, a warning message on dash read "service power steering now".... there were no warning of this problem what so ever and just suddenly happened. Very dangerous and I have read many many others have had same issue with exact make and model of 2010 mercury milan. Please add this issue with power steering to recall list so others don't get hurt. I hurt my neck & wrist when I hit that curb a