What is google play music and why does it constantly load? Why does google play music start up,  and what does it do?

I have some music on my phone but am happy with the basic music player and have no need for or want to access music online.
The issue you are referring too is well reported on Google Support Forums, as it seems to be affecting many users and/or devices.

All points to an update(s) that raised the issue with certain devices.

You can go around this problem until it gets resolved:

Step by step:


Access your device settings;
Touch on "Applications";
Scroll down until you find the "Google Play Music" app;
Touch to open it;
Touch "Clear Data";
If any updates have been installed, on the upper right corner of your screen you should have a "Uninstall Updates" button, touch it to revert to the previous version;  

It may ask your confirmation about going back to the previous/factory version, in that case, confirm the action.


Prevent recurrence:

To prevent this issue from raising anytime soon, you should also disable "Auto Updates" at least until a new update is launch and the reviews are positive:


Open the "Play Store" app;
Touch your device "menu" button;
Select "Settings";
Locate and touch "Auto-update apps";
Touch "Do not auto-update apps".




Quoted answer from Google Support Forum:


  GO INTO PHONE SETTINGS AND SELECT &lt; APPLICATIONS>  SCROLL DOWN AND SELECT .. HIT   AND THEN UPPER RIGHT CORNER SELECT  IT WILL ASK IF YOU WISH TO GO BACK TO OLD FACTORY VERSION... SELECT OK. SHOULD FIX PROBLEM.  ANY APP YOU WISH TO UPDATE MANUALLY UNCHECK ALLOW AUTOMATIC UPDATING. READ THE REVIEWS FIRST TO SEE IF UPDATES AND NEW VERSIONS DON'T HAVE BUGS. GOOD LUCK