Starts then stops. in a loop.

Hi, i bought a s22 ultra off Kijiji knowing that it had issues. The battery had swollen up and starting pressing the back glass off and it wouldnt start. I assumed right away that it just need a battery replacement. I bought a replacement, charging port, and charging main/sub flex cable to cover all the bases. the phone starts (very rarely) but eventually will start, show samsung logo, then turn itself off. sometimes looping, sometimes not. as far as swapping original parts with replacement, i tried all variants of swapping everything but the replacement battery. Do you think its battery thats the problem? i had an issue similar once like this with an S8+, it was the thermister sensor that was the issue. there doesnt seem to be any signs of water damage and aside from the battery, was in very good condition.