Hi! Welcome to the samsung members community!!
Sounds like a network issue tbh.
Go onto google and search for
https://www.speedtest.net/Pay attention to the latency as well as the speed.
Does this happen on both wifi and mobile data? Does it happen on all networks?
Try another streaming platform- Does it lag?
In terms of bluetooth- go to settings- connections- click on the device and make sure its set to audio. On Spotify to the bottom left it should also let you select the device/ your phone