Either a poorly seated tire or a damaged rim can do this. Watch the wheel as it rotates. If the tire seems to hop in one place, but the rim itself does not (watching the rotation as it passes through the brake pads can be a useful indicator), then the tire is not fully seated or too deeply seated at the hop. The fix is to deflate the tire and re-seat it. Sometimes, a hop can be caused by tire casing failure; in this case the tire width changes at the hop, as casing fibers pull apart and allow the tube to expand more. If you find this, you will need a new tire.

OTOH, if you see the rim itself hop as it passes by the brake pads, the rim is not radially trued, or it is damaged. Damage is more likely in my experience, as radial truing problems are seldom abrupt enough to create a perceptible hop while riding. If you find this, take the wheel to a bike shop to see if it can be fixed, and be prepared to buy a new wheel or pay to have the existing wheel rebuilt.