Well I may have made some progress. Since the warrenty is up anyway, I decided to crack it open. I noticed the GPU was getting extremely hot for just sitting at the home screen. So I enabled developer options and turned on some monitoring options (the fact that it stayed on long enough to do this is a miracle in itself).
Right now I have some overlay monitoring on including cpu usage and gpu rendering (on screen as lines). I also checked the "stay awake" while charging option. It's been on about 2 minutes so far, although graphics performance is horrible atm. Almost like project butter is disabled and it's running at half power....that could just be the monitoring overlay though. We'll see what happens...
It made it 21 minutes, but it did reboot again. On restart, the OS smoothness is back to normal, and it does seem like it goes longer stretches without restarting now, however the issue is obviously still there. I should add that the back cover is currently off. which is starting to make me think this has to do with cooling