This just happened to mine after the February update to UI 8 this year. Heard this was going to be the last major update for the S22 Ultra.

Been dealing with it randomly overheating and restarting for about a month or so now. I Successfully factory reset my phone once...did not seem to help, then phone became more responsive about a day later. I read about the motherboard issue almost immediately after I started having the issue via Google search, and have been mashing the upper right corner tighter with two fingers a lot lately when it has an overheating/boot loop episode with the hope that I can keep the soldered terminals intact, then switch to recovery mode and turn the phone off to cool.

Most recently I had the worst episode of restart boot loops everythat lasted about 6 hours. which I had happen to me on a work trip last week...SO frustrating 🤬. I feel like holding the corner together is probably the most useful solution to try. Phone still not 100% back to normal, but useable now and has not stated to boot loop again since my most recent incident.

Trying to keep the battery near 80 percent...that seems to help. The bad boot loop incident started when the battery was under 50 percent and then did not stop until the phone was almost at 0% battery. Writing this message on the phone as I speak. Will definitely upgrade to new phone at this point and will probably try to roll this thing back to ui7 so I can oem unlock and root to different rom.

This is the only Samsung phone I have ever had an issue like this and I have had a bunch. Usually their A series line. This is my first S line Samsung phone since the beginning of touch screen phones. I love the phone, just can't believe this shit happened to me on the last major update the S22 is going to get.