Surface tablets are designed to power on when they detect an external power connection, similar to how a phone lights up when you plug it in. On consumer Surface Go 2 units, there's no built-in toggle in Settings to disable this.
The only related Microsoft feature (Wake-on-Power) is for enabling auto-start on business devices via SEMM/UEFI Configurator — it's not a way to disable the behavior, and it's aimed at IT-managed commercial fleets, not regular consumer Go 2 units.
No software fix exists for consumers to stop it.