Voltage oscillates continously in USB Li-ion charger. Anomaly or CC/CV behavior?
Given no technical information in the question, yes, a normal Li-Ion charger is supposed to turn its output voltage OFF when current drops below certain set point. Having no load certainly meet this condition (zero current). Then the charger needs to check if the battery is present or not, so it turn the power ON and checks for current. An so on. So yes, a no-load charger will do this periodically, aka "oscillates".