Since it is new, it is possible that the bolts holding the wheels in are loose. In the center of the wheels, there should be a screw or bolt that needs to be tightened. If there is no bolt visible, look closer, as there may be a cover to keep grass out.
It is worth noting that I don’t have this exact model lawnmower, but most are pretty similar in design, so please take this with a grain of salt.