Please perform the below mentioned steps to resolve the issue:
1. Check your charging cable (USB cable) for physical damage such as wear and tear, bent prongs etc. If it is damaged then kindly visit your nearest service center to get it replaced.
2. Check charging, if rating is 15W or above. Kindly try to charge the device in a non-inverter socket.
Note: Kindly open Device care from Settings > Battery > Please tap on 3 dots(more option) at the top right hand side > please select settings > enable fast cable charging.
For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).
