Issue in Selenium execution in Jenkins and app engine

I am executing my selenium automation scripts in Jenkins(VM server Slaves).But often the VM servers are going Offline(due to patch update or Schedule maintenance), due to which my scripts are not running on the scheduled time. Also I have scheduled the script in APP Engine, even app engine contains lot of constrains. Is there any other source or way to run selenium scripts with out any issue(Headless Mode). Thank you