SQL Server 2014 SP3 Unexpected Service Stop SQL Server 2014 SP3 CU1 service terminates automatically with the error, 


  Error: 17311, Severity: 16, State: 1.   SQL Server is terminating
  because of fatal exception c0000005. This error may be caused by an
  unhandled Win32 or C++ exception, or by an access violation
  encountered during exception handling. Check the SQL error log for any
  related stack dumps or messages. This exception forces SQL Server to
  shutdown. To recover from this error, restart the server (unless
  SQLAgent is configured to auto restart).


There are multiple instances on the server, but I am having this problem in one instance.

There's not much information in the logs to say why. Do you have any similar problems? What can I do in more detail to find the problem?
You might see a stack dump in error log. You might have hit a bug and would need to go through the logs to find more on it. You might need to apply latest patch CU4. The error message is documente in below link :

SQL Server reports errors for exceptions, assertions, and hang conditions

Too many mights above as these errors are quite tricky and never have just one cause/solution.