EC2 instance reboot/outage?

Hello

if you have the cloudwatch agent, you might be able to see more details about the instance OS
and you could also create a cloudwatch alarm to notify you immediately if there is a status change
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-system-instance-status-check.html#types-of-instance-status-checks

with this, you might be able to go to the OS system logs and find something, cloudwatch agent logs, or cloudtrail
hope this helps
RT