no oil pressure on my dodge magnum V6 1999?

Probably a faulty gauge or sending unit.

Either a faulty gauge or the screen in the oil pan is clogged and when you turned it off it allowed the trash in the pan to fall off and it picked up prime again. Get some crankcase flush and follow the directions to a T. If that doesn't fix it, then you are going to have to pull the oil pan and clean it. Note: If you end up having the oil pan dropped, it would be a good idea to go ahead and replace the oil pump while you are in there. It would be dumb not to.

Either a faulty gauge or the screen in the oil pan is clogged and when you turned it off it allowed the trash in the pan to fall off and it picked up prime again. Get some crankcase flush and follow the directions to a T. If that doesn't fix it, then you are going to have to pull the oil pan and clean it. Note: If you end up having the oil pan dropped, it would be a good idea to go ahead and replace the oil pump while you are in there. It would be dumb not to.

it sounds like either an oil pump is going out or the pressure valve in the oil pump isn't working right because of a sludge build up in it,i wouldn't drive it to much though and it doing this you may have to drop the oil pan to see how bad the sludge is or change the oil pump,if it wasn't rattling when it started doing this it would be a simple fix, like a sending unit,but you are loosing oil pressure if it starts to rattle when it does it,good luck on it,