1997 Maxima has slight drift to the right

Hello all I notice a very slight drift to the right and other times the car rides straight--Some road conditions make the drift to the right more and other times there is no drift... I notice the drift on flat straight roads.. My question is--Are there any issues with the 97 Maxima and the slight problem i'm having? The tires show no stress from this and the air pressure in each tire is equal.. Thanks for any help... Mark

you may need to have an alignment done.

it could also be that the parking brake or another brake is catching slightly...