Check the camera menus for a shutter setting such as "Half Press Release" and make sure it is turned off. On some Lumix models, enabling this causes the camera to fire the shutter as soon as focus is achieved from a half-press.

If your camera has similar release/focus options, review those as well and return them to normal shooting behavior. Since you already tried a factory reset, it’s still worth checking because some settings may need to be confirmed manually depending on mode or menu group.

If you cannot find that option or changing it does not help, the problem may be a mechanical fault in the shutter button switch, where the camera is detecting a full press too early. In that case there may not be a practical settings-based fix, but checking the release-related menu options is the first thing to try.