restrict-user-to-instance.json

{
     "Version": "2012-10-17",
     "Statement": [
        {
           "Effect": "Allow",
           "Action": "ec2:DescribeInstances",
           "Resource": "*"
        },
        {
           "Effect": "Allow",
           "Action": [
              "ec2:StopInstances",
              "ec2:StartInstances"
             ],
           "Resource": "arn:aws:ec2:<region-name>:<aws-account-number>:instance/<instance-id>"
        }
     ]
}