Welcome to Android Central! You can often get an idea by looking at the battery graph in the system settings -- a restart may look like a brief interruption in the battery graph.
Try booting into Safe Mode as well, and use the phone for a day that way. Does it still restart on its own? If not, then something you installed is probably causing instability.
https://www.t-mobile.com/support/dev...note10-plus-5g
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