98 suburban oil pressure gauge

ok, lets see. My oil pressure gauge has just started acting kinda funny, when im sitting still it goes to about 0 check gauges ligght comes on. When i accelerate it goes up to 40 when i come to a stop about 20 with a idle around 500 . When i go to start again it drops to 0 check gauges light comes on and then pretty much right away goes back up to 40 and check gauges light goes off as soon as pressure picks up. Im wondering if it is a sending unit or something???? Any help is much appreciated.

Had similar problem with my 88, it was the sending unit, shorting out and melted the plug in wires.
Changed the sending unit, repaired wiring and back to normal. Good luck