boot loop or bad battery?

ipad pro 12.9 seemingly in a boot loop, but I have a sneaking suspicion of what it might really be.

Backstory: I bought an iPad Pro from a college kid. he informed me that it was very finicky with the charging, that it was intermittent when it worked, and then right before I bought it, it quit charging altogether for him.

well, that one was pretty easy. replaced the usb port/ribbon connector and bam. it starts charging again, and I have a great iPad pro for $50.

well, the other day it quit charging again, so I figured I messed up the install somehow. opened it back up, tested for power, that part was solid. but then last night I plugged it in just for funsies, and it is doing what appears to be a boot loop, but none of the troubleshooting tasks I know of or could find remedied this issue like they normally would.

I plug it in, and the apple logo appears like it’s booting up - for about 3-5 seconds, then powers off. repeat this cycle over and over is all it will do. I can’t force reset, I've tried to open diagnostics with the volume button/plugging in and all that, but it won’t get that far. and last night, I’m not sure if the force restart was successful or what, but the cable and MacBook icon came onscreen as if to say connect iPad to Mac. I have not done that part yet, becasue I just now remembered that piece of info.

I don’t think it’s an actual boot loop, so my question is: Would a failing battery do something that emulates a boot loop in this way? won’t really hold enough charge to start up completely maybe? is there a way I can know for sure?

Thanks in advance for any insight.