Google music player queue
If you want to play selectef songs back to back it is recommended to create a playlist of the songs you tend to listen more often. It is quite easy way and reliable as well.

Add to queue is nothing but to add the songs it is showing right in the list.

If you want to play few songs at once back to back please choose 'play next' option, as your concern is by choosing 'play next' option let's say for 5 songs, your 5 songs will listed just below your currently played songs and after 5 songs you will see list of all the songs from library.