Vios steering vibration spongy handling

Interesting. I had similar symptoms on my old Opel Corsa, although the shaking wasn't as pronounced initially. Could be a few things. How's the steering fluid level? Any unusual noises when you turn the wheel at low speeds? Has the problem developed gradually, or did it appear suddenly? A defective pressure hose can manifest similar issue

Fluid level seems normal, and no weird noises that I can hear. It did seem to get worse over a few weeks. What ended up being the cause with your Corsa?

Ah, gradual worsening points away from sudden catastrophic failure, doesn't it? In my case, with the Corsa, it was a corroded electrical connector on the electric steering system. I would suggest visiting a workshop.

Thanks for the help! Turns out it was a loose cable/plug connection. The workshop charged me 95€ to fix it.