If the engine sound right and the oil level is right, the engine oil pressure sending unit may be defective or the wiring connector loose? It is rare to have a defective oil pressure sending unit with Camrys. Frankly speaking, I've never seen such a case with a Camry. A few similar cases I came across with Camry, Highlander, Sienna, Corolla were: the engine oil were very low and after adding oil to proper level, the light were off and no further oil warning problems. I have seen a few Tundra and Sequoia trucks with engine oil pressure problem on the combination meter display. After replacing the oil sending units, the problems were fixed.
However, what I say above is only very general comment. As to the specific reason of the problem, actual inspection is necessary.
