SQL Server not starting at Windows startup but starts manually
This issue happens because the SQL Server lost the logon id credentials or used an account without rights to start services.

For starting your services automatically, SQL Server needs an account with rights to start services during operating system start up.

To solve this issue you need to go 
Administrative Tools > Services > SQL Server(MSSQLSERVER or the name of your instances) > Right Click >  Properties > Move to Log On > Set the Log On option using a Local System Account

If you have chosen this option, hit on Browse Button and find the Local Service Account or Network service Account there > Click in Apply. 

Restart your computer and you will able to start your SQL Server.