Yep, I have the same issue.
I can create a character with the character-creator, but once I'm finished and have pressed the "PLAY NOW" button, I'm shown a quick load-screen and after that the computer crashes and performs a hard reset. I can't even get into gameplay because it will always crash my computer. There is no crash-message or anything, it just goes black and reboots. I'm on an older Dell Laptop, but as far as I can see it should be able to run the game just fine... I've updated my OS and all GPU drivers, but it didn't help. The only thing I could imagine is that this is indeed a power-supply issue (I think my AC-Adapter that runs my laptop has an output of 130 Watt? This seems ludicrously low, but I suppose it's normal for laptops?), but I've never experienced anything like this before and never had issues with other games.
My specs:
DELL XPS 15 (9550) Laptop
CPU: Intel Core i7 (6th Gen) 6700HQ / 2.6 GHz
RAM: 16 GB DDR4 SDRAM
GPU: NVIDIA GeForce GTX 960M - 2 GB GDDR5 SDRAM
I've waited ages to play Bannerlord and am currently thinking about buying a new PC for this game.