Unsure unfortunately. It's random. I crashed three times today within an hour. I have checked my Switch 2 for overheating and it is absolutely fine.
I tried to take video clips each time but stupidly hit the A button on the error which takes me back to the Switch 2 home menu, this does not allow me to make a clip of the previous 30 seconds. I will update this post if I manage to capture the issue.