A few months ago my Avalanche popped up a message that said "LOW OIL PRESSURE - STOP ENGINE". I looked at the gauge and sure enough there was no oil pressure. I let it sit for a bit, started it and pressure came up close to normal. I was a few miles from my house. I drove it about a mile, pressure dropped again. I let it sit, repeated the process a couple of times but I finally got it home without running it very long with low pressure. I changed the oil (it was due anyway) and filter. I think something had happened with the filter. Don't know if it collapsed or came apart, but once I changed the filter the pressure was back to normal and it hasn't done it again since. Oil looked fine.
Which reminds me - I need to change out the oil pressure sensor on my motorhome. It reads 60 PSI all the time - it would be good to know what the oil pressure actually is.