the oil warning light has started coming on and off but the oil is full! on 2007 Chevrolet Impala

the oil has been changed regularly and there has been no problems now light will come on some times and alarm will sound maybe a few seconds or a few minutes only every now and then ,where do I start?

Asked by for the 2007 Chevrolet Impala
Replace/have replaced, the oil pressure switch or sending unit, as some call it. Special tools required!