Well the A20 was released in 2019
So it could be the battery needs replacing.
But do check battery stats in settings to see if an app or Theme is using more than it should.
If you haven't restarted the phone for some time, this can help as it shuts things down and helps to optimise the software
Wiping the Partition Cashe on the phone can help as well
All this is assuming your charging setup is working correctly as well
