Why SQL Server SPID is blocking itself

Hi All

Issue: SPID is blocking itself

Description: On one of our server SQL 2005 i have run one maintainence (update statistics)job in morning hours on a businessday and as it should not create any issues i was monitoring server health. After executing job i found spid 64(belongs to job)  is blocking itself.and after some time it went off

How to restore system databases on lower build

knowledge sharing : Restoring System databases on different build

Issue :

Datafiles and log files are lost on Uat server  due to OS issue
------> Sql server is down
------> All data and log files lost including system database
------> Only backups are available