Here i am sending you the Event IDs and errors as sever restarted automatically once..i am just concern that these errors could be the cause of the server restart, please check this errors and solutions to resolve these errors so it cant come next time.
1 System Error (On event Viewer)
Event ID : 36888
Event Source : Schannel
Error : The following fatal alert was generated: 10. The internal error state is 1203.
2 System Error (on event viewer)
Event ID : 10009
Event Source : DistributedCOM
Error : DCOM was unable to communicate with the computer PCOF05.mydomain.local using any of the configured protocols.
Keyword : Classic
3 Application Error (On Event Viewer)
Event ID : 6398
Event Source : SharePoint Foundation (it is critical Error)
Error : The Execute method of job definition Microsoft.SharePoint.Search.Administration.SPSearchJobDefinition (ID fa9e2d0a-9b07-4684-ba91-80dc5759f546) threw an exception. More information is included below.
The device is not ready.
Note that this is the only server sbs 2011 server on the network and there are 7 computers connected to it. all computers are in the same domain. we have act 2011 pre. software and database installed on the server so i have created 3 firewall rules on the server to allow the local computers to connect the act database.