What would cause oil pressure to randomly drop to zero then go back to normal?

What is your question?

About after driving the car for about an hour on the highway, it will drop pressure for a minute then come back normal. the car has oil and has been changed every three months as i only drive maybe a hundred miles a month. replaced the oil sending unit. it will happen rarely in town now after driving for a few minutes. inherited the car from grandma who only drove the car six months a year on Fridays 20 miles highway to town to grocery shop, then park the car in a garage for the winter for six months.

What makes this problem better or worse?

it seems worse after engine is hot.

How long has your 1994 Lincoln Continental had this problem?

a year