Yaris Hybrid XP13, spongy suspension from 120km/h??

Hey guys, I’ve been on the highway again after several weeks and from 120km/h the bumps in the road have made themselves felt very well. I didn’t drive normally, but more like a boat that “swings” over the water. I can describe this badly.. it’s like the car was tickling over the highway, so a big swing part. Does anyone know what I mean? The problem is, I have the feeling I’m losing Traktio Can you counteract this? I thought if the car had a lower center of gravity, shouldn’t that be the case with lowering springs? Or is it perhaps because of the “soft” winter tires? Does anyone have experiences with it or already have lowering springs in their new Yaris? L.G.