iPhone 8 turns off abruptly

1. Fully charged, unplugged and then abruptly turn off within 2 minutes while using. Can't turn on unless plug in charger. Updated to iOS 14.5.1. Already tried reset, and restored using Mac. Battery health 80%.
2. This above is the latest issue in my phone, besides other issues since I purchased in 2018; screen turn off while using, can unlock screen without needing finger print sometimes.

I already checked Serial Number several times for replacement program and it says not eligible.