sql server restart time

Option 1:

SELECT sqlserver_start_time FROM sys.dm_os_sys_info

Option 2:

sp_readerrorlog 0,1,'Copyright (c)'

Option 3:

 SELECT create_date FROM sys.databases WHERE name = 'tempdb'

Option 4:

SELECT login_time FROM sys.dm_exec_sessions WHERE session_id = 1

Option 5:

Right click on the server name and look for the reports > standard reports > Server Dashboard

Finding out who restarted the sql:

SELECT  TE.name AS [EventName] ,

        v.subclass_name ,

        T.DatabaseName ,

        t.DatabaseID ,

        t.NTDomainName ,

        t.ApplicationName ,

        t.LoginName ,

        t.SPID ,

        t.StartTime ,

        t.SessionLoginName

FROM    sys.fn_trace_gettable(CONVERT(VARCHAR(150), ( SELECT TOP 1

                                                              f.[value]

                                                      FROM    sys.fn_trace_getinfo(NULL) f

                                                      WHERE   f.property = 2

                                                    )), 4) T  -- 4 is the default number of trace log files

        JOIN sys.trace_events TE ON T.EventClass = TE.trace_event_id

        JOIN sys.trace_subclass_values v ON v.trace_event_id = TE.trace_event_id

                                            AND v.subclass_value = t.EventSubClass

WHERE   te.name IN ( 'Audit Server Starts and Stops' )