They will not start automatically. You will either have to manually start the VMs or else use some automation such as an automation account (with scripts to start the VMs) or else use a logic app with a Start VM workflow. This is the easier approach of the two to setup.
This video will show you how to set this up:
https://learn.microsoft.com/en-gb/shows/IT-Ops-Talk/Auto-Shutdown-and-Auto-Start-an-Azure-VM