Yeah, you're oil pressure sensor is crapping out. It takes too long to sense there is no longer any oil pressure there, so when you turn the key on again, the system notes that the sensor is already open circuit and reports an error.
After dealing with this through several sensor replacements, I've come to the conclusion that not all oil sensors are equal. Call me superstitious, but I now replace them with the genuine part. Otherwise, they come back to haunt you.