In reply to srbeeram:
https://verificationacademy.com/verification-methodology-reference/uvm/docs_1.1d/html/files/seq/uvm_sequence_base-svh.html#uvm_sequence_base.start
You will see the start() task calling body().
I think I misspoke earlier. The sequence arbitration with the sequencer comes from [font-courier new]start_item(). It blocks calling [font-courier new]sequencer.wait_for_grant(this, set_priority);.