When charging the cell phone via charging cable, it will disconnect and reconnect rapidly.

When you face that disconnect and reconnect problem while charging the phone (like below video clip), you could try to follow the troubleshooting steps listed below:

1. Clean the charging port of the phone or the golden finger of the cable to make
       sure if there is any dirt or debris.

2. Try to make sure if the cable has some loose wires or if it does not fit properly
        to the charging port of the phone.

3. Try to confirm the charging accessories you used (like charging cable、
        charger、 power bank or USB charger outlet…etc) if the power supply of them
        is sufficient, you could try to use different charging accessories to check if the
        same issue  still occurs. 

4. To make sure if the” Optimized Battery Charging” function of your iphone is
        enable that it might delay charging. 

※With iOS 13 and later, when Optimized Battery Charging function is enable, your iphone will delay charging past 80% in certain situations. This feature is designed to reduce the wear on your battery and improve its lifespan by reducing the time your iPhone spends fully charged.