Oil Pressure gauge on 2000 Chevrolet 3500 Pickup

When I am driving my oil pressure gauge dips to zero, the light comes on and then shortly after the gauge goes back up to 20 or so. Does this off and on while driving. What could be the problem? No overheating or other issues. Thanks.

Asked by for the 2000 Chevrolet 3500 Pickup
The oil pickup screen may be clogged as well causing the intermittent pressure drop/rise. If the pressure switch dosen't solve it, this will be the next place to check.
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I would suggest a oil pressure switch first? If it still does the same thing have the oil pressure check out.