Can't find reboot reason

Good day,

Reviewing your instance I can see that it failed system health checks and this issue was caused by our AWS hardware side as the host holding your instance was impaired but then the host got fixed and became healthy again.

I hope you can understand that from time to time our underlying hardware may encounter issues, we try to minimize the effect but sometimes our customers may experience issues with it. When system issues of this nature occur, our dedicated Infrastructure teams thoroughly investigate the cause and architect system improvements. The details of this process are kept highly confidential in order to protect our AWS platform and customers. Although we cannot share specifics on the root cause of the failure, I can assure you we are taking every possible measure to mitigate such issues in future.

For more information regarding the status checks of EC2 instances and the difference between System and instance health checks, please review this link:
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-system-instance-status-check.html

Thanks,
Abdallah