DS4 Steering Vibration and Spongy Handling

Sounds familiar. Had similar symptoms on my old Opel Astra, though the mileage was lower. Is the steering heavy at all speeds or just low ones? It could be the steering pump, though a connection issue is more likely.

Mostly at low speeds, yes. When you say connection issue, what exactly are we talking about? Steering column?

Could be, but in my case it was a corroded plug on the pressure hose sensor. Either way, better get it checked professionally, I ended up at a shop, and it was worth it.

Cheers. Turns out you were right. Garage found a defective plug connection. 95€ fixed it. Thanks!