In order to have Adagio launch without even visiting the login screen, you are required to use the parameters for the data location and extension, even if you only have one. Defaulting only the user ID and Password leaves you with what you are getting - all the fields filled in, including the last accessed company data - but having to press Enter to continue.

You need to add /dX:\datapath /eyyy at the end where X:\datapath is the location of your data and yyy is your specific data extension.

There is some information in the help file if you do a topic search on 'command line parameters'