Why my car Low oil light sometimes comes on when I start the car.?

Sometimes it will come on when i start the car and then the other times it wont come on. I checked the oil and its full. What could be the problem? I have a 1990 buick rivieraWhy my car Low oil light sometimes comes on when I start the car.?
When you first start the car, it takes a few seconds for the oil to circulate and build pressure. The light will be on until this happens. If you are using a fairly heavy grade of oil, it will take longer for the cold oil to build up pressure. If the car is in good condition, runs well with little oil consumption, I would use a 5-W30 semi-synthetic oil, and see what it does.Why my car Low oil light sometimes comes on when I start the car.?
My car would do that because I parked on an incline.
a sensor
the oil sending unit is probably getting ready to go bad.

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