Spotify automatically starts when loggin into computer even though in player settings it's set to DO NOT start automatically when logging in. Only way to disable Spotify auto-start is to disable it in startup task menu in Windows.
This bug appeared when updating to version 188.8.131.523, which was released on 4th of July 2017.
Solved! Go to Solution.
There isn't anything in C:\Users\USERNAME\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup folder.
However, in System Configuration under Startup items there is a new entry (C:Users\NAME\AppData\Roaming\Spotify\Spotify.exe --autostart) command with the recent updated version 184.108.40.2063.
Prior to the update (C:Users\NAME\AppData\Roaming\Spotify\ Spotify WebHelper.exe) command entry was the only thing in startup.
Edit: Found a workaround to the problem. In the player settings under "Startup and Windows Behavior" disable "Allow Spotify to be opened from the web". That should get rid of any Spotify command entries in Windows Startup.