I am noticing large mounds of soft dark sand in the grass and there are tunnels leading to and away from them. These tunnels seem to be maybe two to three inches deep because my cane tip sinks into them. These mounds are 4 inches in diameter and around an inch to an inch and a half high. The area in which this is taking place in is a twenty five feet square. These mounds seem to be formed at night and appear in the morning. I do not see any bugs or anything.
It could be a vole or mole problem. They may not be burrowing, but rather just digging holes to look for food. They are nocturnal animals, so it is likely you would not see them. Here is more information on controlling these rodents: https://www.gardeningknowhow.com/plant-problems/pests/mole-control-home-remedies-for-removing-moles-from-your-yard.htm