Just in case there is an App hogging resources, causing Heat issues, causing lag, Battery drain or freezing, clear your recent apps, also try setting 3rd party apps to Optimize in Settings Battery, only leave the ones you need run in the background or to notify you such as messages, email, Google Services, oneplus etc on Intelligent control.
Android may take a few days to optimize those apps after setting them to Optimize depending on your usage of those apps. A10 has its own learning curve.
Go through 3 to 4 charge cycles, leave on charge beyond full capacity for a couple of hours. Preferably overnight.
After a few days, Check App battery stats at about 50% and see if there are particular apps using more resources than necessary.
A definitive guide to everything that affects smartphone battery life
https://www.androidauthority.com/smartphone-battery-life-drain-causes-1071423/
Charging, battery, performance, caches and battery calibration myths busted
https://forums.oneplus.com/threads/...-and-battery-calibration-myths-busted.993896/
If its still not improving, backup your phone, full factory reset, Delete All Data, as in wipe your phone completely, and repeat the steps above.
This will restore you to a fresh installation of Android. So you will need to backup your phone.
After Backing up the phone.
Go to Settings,
System,
Reset Options,
Enable Erase Internal Storage.
Then click on the Delete All Data button.
For more info on how to backup your phone, check the solutions here.
https://www.androidpolice.com/2020/05/14/how-to-back-up-your-android-phone-before-a-factory-reset/
And here
https://www.androidauthority.com/best-android-backup-apps-and-other-ways-too-608014/Click to expand...