Is unwrapped refrigerated cheese safe?
It is almost certainly safe unless it was left out at warm temperatures to spoil, or has molded, or otherwise spoiled in a manner not directly related to being uncovered.

It may, however, be unpalatable due to:


Drying out
Picking up flavors or odors from other items in the refrigerator


Since you are eating it relatively quickly, if you are not experiencing these issues, your practice should be just fine.

My own personal preferred method is to put my cheese chunks in a zip lock type bag, which substantially cuts down on the drying, especially for moister cheeses like mozzarella or semi-firm cheddar.