Peugeot 406 1.8 petrol shaking at speed?

If a Peugeot 406 1.8 petrol is shaking at speed, it could be due to several issues, including unbalanced wheels, misaligned tires, or worn suspension components. Additionally, problems with the engine or transmission mounts can cause vibrations. It's advisable to check the wheel balance and alignment first, and if the problem persists, have a professional inspect the suspension and engine mounts for any wear or damage.