High-speed instability on my EcoSport – car drifts left-right even with straight steering.

My EcoSport (~70,000 km) has been giving me a frustrating issue lately — at higher speeds (above ~80 km/h), the car starts wandering left and right even when I’m holding the steering straight. It doesn’t pull consistently to one side, it’s more of a nervous, unsettled feeling on the highway.
I am diligent with balancing and alignment. Both of these were done before a long drive still the issue persisted. The car runs great in city roads and even in high speed undulated roads I feel nothing is off. Its only on straight roads with no undulations I feel this weavy feeling

Please suggest