How to stop iPhone resetting shuffle.

[JM44]

Couldn't find anything related to this. I shuffle a playlist at work, which is all fine and dandy until I pause it to go for lunch break, which is around 45 mins. When I return to work and go to resume the playlist, spotify has effectively restarted and I have to restart the shuffle, which obviously means I will encounter various repeats of songs I have already heard. Any ideas how I can change this?