Is there a specific task displayed it is hanging on?
After boot, is there anything in the vmkernal logs that provide some idea what task is causing this?
Do you have any VMs using RDMs? If so have you perennially reserved the RDM LUNs?
Just to eliminate the environment issue (like storage device scanning etc), remove your HBA cables from the host and try to boot and see , this will help us to isolate the issue.