Tramlining is the phenomenon described in the posts above. It's when the car follows cracks/grooves/ruts in the road. The car tends to veer/slide in the direction of the road imperfection until the tires regain proper grip and continue forward. It can be unnerving if you haven't experienced it before. Things like wide tires with stiff sidewalls just magnify the effect.
https://www.tirerack.com/tires/tiret....jsp?techid=47