The touch-sensitive switching and dimming of your Salt&Pepper can be influenced by several factors. The conductivity of the surface, for example, plays a role here. If you hold the light in your hand, it will react differently to the touch than if it were placed on a wooden table, for example. Other, particularly older, electrical devices nearby can also influence the touch. However, Salt&Pepper always adapts to the current conditions. If you change location, Salt&Pepper will recalibrate after about a minute.
While you are charging your Salt&Pepper with the power adapter, it may occasionally respond very slowly to the touch. This could be due to your power supply. Once charging is complete, it will react as you are used to.