SQL Server Services - Stopping Randomly

Hi, 

The SQL Server services (MSSQLServer , Agent service) seem to stop randomely from time to time. I have no clue as to why this is happening. My agent service seems to have stopped 4 days ago, and I was not aware of it, although sql server itself seem to stop occasionally at which point we cannot access it from Management studio.  (I have to manually restart services at this point)

All I can see in the SQL Server Logs is:

Message
[360] SQLServerAgent initiating shutdown following MSSQLSERVER shutdown

Message
[359] The local host server is not running

Could someone help me out on this?

Thanks

Pramod