By default, the driver only runs once when you use the UniPHY example project.
To make the driver run continuously, modify the driver file at the location "<variation_name>_example_design\example_project\<variation_name>_example\submodules" named as either
driver_avl_use_be_avl_use_burstbegin.sv or driver_avl_use_burstbegin.sv
Change the following line
defparam driver_fsm_inst.NUM_DRIVER_LOOP = TG_NUM_DRIVER_LOOP;
defparam driver_fsm_inst.NUM_DRIVER_LOOP = 0;
This change will enable the UniPHY example driver to run continuously.