SQL server won't run my Maintenance Plan unless I start the AQL server Agent

In SQL server management studio I have to go to SQL server agent and right click and click start, and then the maintenance plan will run, but after a reboot it won't run again until I start it again.  How can I fix this?

This is the error I get if I try and execute the maint plan when the agent is not running?

TITLE: Execute Maintenance Plan
------------------------------

Execution failed. See the maintenance plan and SQL Server Agent job history logs for details.

------------------------------
ADDITIONAL INFORMATION:

An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)

------------------------------

SQLServerAgent is not currently running so it cannot be notified of this action. (Microsoft SQL Server, Error: 22022)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=09.00.3068&EvtSrc=MSSQLServer&EvtID=22022&LinkId=20476

------------------------------
BUTTONS:

OK
------------------------------
Start Free Trial