Originally Posted by N8N
Flushing the PS fluid was my first thought as well.
Not exactly pertinent to a BMW, but a buddy of mine bought a '64 Studebaker GT Hawk that'd been sitting a while. It ran and drove but the power steering was damn near nonexistent, and when it did work, it felt "notchy" like the OP describes (but probably more so.) We unhooked the return line from the P/S pump reservoir and stuck it in a bucket and ran the engine while pouring ATF in the reservoir and sawing the wheel back and forth. Did that until the fluid was nice and pink and then some for insurance, reconnected hoses, topped up and worked the wheel back and forth a couple more times with the engine running to get the air out. Worked fantastically after that!
Mine only acts up occasionally while parking. Yes they checked it.