SQL Server 2014 SP3 Unexpected Service Stop
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.