Look a little closer
A doorknob zap happens when charge built up between your body and the knob moves all at once. The very brief discharge acts like a tiny lightning bolt and stimulates sensory nerves in the skin.
Charge can transfer when different materials touch and separate. Walking on carpet or rubbing clothes repeats that contact, leaving one surface with extra electrons and the other with a deficit. Friction increases the number of contacts; it does not create electric charge from nothing.
Insulating materials such as rubber soles and many synthetic fabrics block an easy route for charge to escape. As the electrical potential difference between you and nearby objects grows, a metal handle offers a much better conducting path.
If the difference becomes large enough, air molecules can ionize before your finger touches the metal, forming a momentary channel. Charge rushes through the channel and skin, producing a spark, a click and a sharp sensation. The voltage may be high, but an everyday static event stores little charge and usually ends almost instantly.
Static is more noticeable in winter and dry rooms for the same reason. Moisture can form a thin layer on surfaces that lets charge leak away gradually. Dry conditions remove much of that path, allowing an imbalance to persist.
Moderate humidity, less static-prone fabrics and frequent contact with a grounded conductor can reduce large zaps. Household shocks are usually just annoying, but electrostatic discharge can damage sensitive electronics or ignite flammable vapor, so controlled environments require dedicated grounding and antistatic measures.
