I had an AstraVan once that used to lose power steering randomly mid corner. Turning it off and on again reset it.
It was under warranty, Vauxhall refused to fix it as it was always working when I took it there. Eventually I kerbed it badly when I didn’t quite make a corner. left it running so the fault remained and dragged to the dealer. They fitted a bigger alternator apparently.
It then started happening on startup, rather than mid corner. I found the Alternator connections were loose.
Was fine after that.
For those that haven’t experienced it, broken power steering is usually way worse and notchy compared to a manual rack.