[Bradical]

Your oil pump is loosing its prime. The noise is from the oil pump running dry for a bit, most likely. With the engine cold, remove the oil filter and pour a little oil down the hole and screw the filter back on. If you have oil pressure right away when you start it up, then replace the oil filter and be on your way. I would recommend replacing the oil pump drive gear because its probably a little worn from being started dry a few times.

I suspect the oil filter check valve isnt working.