Hi all. I have a 1999 dodge ram diesel. Today I drove it for 45 minutes and it ran fine. I shut it off for an hour and when I started it back up the oil pressure guage went to 0. It stayed there for a minute then went back up to normal. Then a minute later it went back down to 0. I shut it off and checked the oil which was good. I decided not to drive it home so I left it there. What might the problem be? Is it safe to drive home? Thanks.