Try unpairing and re-pair your AirPods with your phone, and charge your AirPods to maximum capacity. Also try restarting your phone. If this doesn't work, check the ports inside the AirPods, such as the charging contacts, the Lightning port etc. for dust and other particles that are blocking them, clean them with bristle brushes and cotton swabs (see second link below), unpair and re-pair your AirPods again after this. If the problem still occurs, go to an Apple Store and ask for help, they will probably help you switch an AirPod (but you will have to pay, as most AirPods 1 are out of warranty, because they were launched more than 3 years ago). This problem is probably a connection problem either between the AirPods (the two earphones) or between the AirPods and your device. AirPods 1 have Bluetooth 4.2, while your iPhone 11 has Bluetooth 5, this also may be a compatibility issue.
Hope this helps!
Links to help:
https://support.apple.com/en-us/HT209581
https://support.apple.com/en-us/HT208729
https://support.apple.com/en-us/HT209463
https://getsupport.apple.com/?caller=kbase&PGF=PGF32003&category_id=SC0285
