I think there is a setting in Spotify to "normalize" all the tracks in a playlist. But if you are not using playlist, but selecting songs from different albums, then it will not work.
Different volumes streaming Spotify
I stream Spotify and I'm fairly happy with it. When I listen, each song is at a different volume and I'm constantly adjusting the volume on my iPhone. Am I doing something wrong? Can I resolve this. I greatly appreciate any advice. Doug