Next time it happens open the Task Manager and see if bdb_wp_engine.exe is still running. If it is, your not going to get an error log because something else is causing the program to stop responding in a way that doesn't behave as a full on crash.
It happened to me a lot in one factory. It was due to how the server was disconnection sessions. Never could fix the problem. In the end I just asked the IT department to setup a virtual machine just for running the databases.