I feel a vibration whenever I slightly run my fingers on the side of my phone while it’s charging

I have an iPhone 11 and recently, I noticed that whenever I would set my iphone down and run my fingers on the side of my iphone while charging, I can feel a vibration. I tried running my fingers again while my phone was charging but isn’t set down (I’m holding it), I can’t feel the vibrations anymore. I’m using the original Apple 20W charger. I’m thinking that the culprit might be the slightly rusted lightning connector I used for charging my phone with a power bank. Is this normal? Please help.