I am having the same issue from the past 2 days since the last Bose soundtouch app update.
I have never had this issue before.
App version 15.120.23 and Interface version 17.170.81.
I though it was a problem just with my spotify but has been happening with Pandora too and the preset stations on my Bose soundtouch 10 speakers.
Very annoying!!
Try rebooting your router and see if that helps. Sometimes I get a lot of buffering when watching a Netflix or VUDU movie that goes away after I reboot my router.