iPhone 8S cable falls in and out of charging.

Remove any debris from the charging port on the bottom of your device, then plug your charging cable firmly into your device. If the charging port is damaged, your device probably needs a service. Let your device charge for half an hour.

If your iPhone or iPod touch won't charge - Apple Support (IN)

It seems like it, yes. If this happens with multiple cables to see if it is not a faulty cable. If not Please Contact - Official Apple Support to set up hardware service