Description of my problem. Skoda Octavia 3 2018 year 2.0 tdi 4x4 station wagon, 215000 km. The problem started last September. At low speed 45-50 km/h a bouncing (slight shaking) starts in the rear of the car, as if you have a crooked tire and with increasing speed the amplitude of this bouncing increases. Outside the city on a flat road at 100 km/h it is still felt, but as I said more subtle. It is not felt in the steering wheel, but in the driver's seat and on the floor, but the child when he was in the back seat confirmed that he felt it under him. I have already been to 5-6 service stations, and everyone says there must be something, but they shrug and do not know what the reason is. Tires and rims, balance are excluded, because it does it with both 18 inch summer and 16 inch winter, I even took his 17 inch from a friend for a test. I took it to a Å koda service station, they suspected that the front inner bearings were a little broken and that it was transmitting vibrations, so we replaced them at another service station with SKF and also replaced the engine and gearbox mounts because they had started. There was no effect, the problem continued. Upon inspection at several service stations, as I already said - the flywheel is fine - there is no noise, no noise, the pads on the entire car are fine, the cardan bushings have been checked and they are fine. The car has been serviced from start to finish - the gearbox with original oil, the Haldex has been serviced and the strainer has been cleaned, oil filters, antifreeze, Kayaba front shock absorbers have been replaced. There is no whining from the gearbox, Haldex and so on. The interesting thing is that when the car is cold, for example, it has not been driven for 2 days and I get in the morning and start driving, the bouncing is stronger, when I drive the car for 5-10 minutes it decreases and starts to be felt more easily. Another interesting thing is that when the car is lifted on a lift, because as I said we have done this several times already and for example we change the tires, this shimmy almost disappears and after a short ride of 5-10 km it appears again. The rear axle shafts look in excellent health and have no play - they were also looked at in the service station, the only thing that I know is funny but not really necessary are the rear discs and pads in the sense that there is still life in them, it's just that when I got the car it was clearly sitting without being driven and they were rusty. I'm looking for advice from someone who has suffered with a similar nonsense because I don't know what could be the cause anymore? Thank you!