What causes severe shaking when starting a cold BMW?

[SanMatteo]

BMW experiences severe shaking when starting cold due to the following reasons: 1. Severe engine carbon buildup: When there is excessive carbon buildup inside the engine, the gasoline sprayed by the cold start injector is largely absorbed by the carbon deposits, resulting in an overly lean air-fuel mixture during cold starts, making it difficult to start and causing shaking. 2. Ignition system issues: Poor performance of the ignition system, such as spark plug misfiring, can lead to severe shaking when starting the car cold. 3. Unstable fuel pressure: Abnormal fuel pump supply pressure or incorrect readings and poor performance of the intake pressure sensor can cause body shaking. 4. Aging engine components: Worn-out components leading to engine mount issues can transmit vibrations to the steering wheel and cabin, causing shaking at idle.