There are some people here that had a similar issue (including me), I myself had to get a new device (replacement) from Google to solve that issue. We already had/have a thread about this, maybe you can find some info there.
I had the same issue before but this is what I had done before and after, so I hope this advice may help you.
I had come from a OnePlus 8 Pro, so I naturally wanted to transfer all data from 1 phone to the other. BIG MISTAKE! I had several reboots during the 1st few days. So I started searching around this forum and found a few people suggesting that you factory reset your phone but DO NOT TRANSFER any data from your old phone to your new phone (using the cable). Instead, factory reset your Pixel 6 without restoring any data, then once you get through the initial setup, upgrade to the latest version using an OTA file. Once you did that, then start slowly manually transferring the data from your old phone manually. This is what I did and have had no issues since, no reboots and everything seems solid. Battery life seems way better doing is this way and the UI seems more stable as well, as before, it would be janky and the battery would drain.
I hope this helps