Negative oil pressure??

92 318 Dakota 90K miles Just started noticing this on cold mornings. When I first crank it up the oil pressure guage dives below zero, as far as it can go. It stays there 4 or 5 seconds then begins climbing towards normal.

No audiable bearing knocks or rattles.

Any suggestions appreciated.

Thanks

So many Garys and Clydes ..so.. "Leroy"