Password changes for no apparent reason

My password changes from time to time, with no apparent reason.   This occurs so that I cannot access email from any device.  I have had to have password re-set multiple times by Verizon, which always take an hour or so before all done, by phone.   Is this occuring to others?   Is this a result of others trying to break into the account?

This always occurs, as luck happens, when I am urgently trying to retrive travel or other informaiton sent me.

Why do passwords reset themselves?