Low Oil Pressure

At low Speeds below 10 MPH and idle only does the low oil pressure oil light
come on before i got a oil change it would stall out at stop lights and at idle
which it don't do anymore... From a cold start it does not have any oil
pressure light on..
when the low oil pressure light comes up.. what could be causing this ?
is this just a minor issue? had oil light sending unit replaced last year that
didn't fix the light. But after a oil change the car don't stall out anymore when
the engine is hot at stop signs, red lights and idle.. Low oil pressure light
comes on when engine is hot only.. 90,448 miles and counting on the
car started having this issue at around 85,000 thousand miles car has had
this issue well over a year.