Here is the permanent fix for this issue. Go to settings, apps, click on spotify, click on battery. Then click on optimize battery usage. There will be a drop down menu at the top of the page that will let you click All. Then scroll down to spotify and toggle the slider to your left to where it is off. This should fix your issue. Happy listening!
Idk if you figured out how to fix this problem yet. Here's how to fix it, you need to go to settings. Then search for sleeping apps, once you do that you need to make sure spotify is not one of them. If it is take it off. Once you do that problem fixed :)
This is also an issue with my S10. The Optimize - manually select power off button trick does not work for me. I also ensured that Spotify may run in the background (not in the sleeping apps) NOTE: it doesn't permanently remain off. It "pauses" and will start playing again. It does this throughout its time with the screen off and the pauses are significant. Like others, if this can't be resolved soon, I'll drop my Spotify premium subscription. There is no other music app that has this issue. Amazon music is fine. UPP app is fine. What's the problem with Spotify? Doesn't matter if the music is local or not. Overall, I love Spotify but this is intolerable (especially in the midst of workouts).