I have a question. The server shuts down the server every 30 to 1 hour for no apparent reason.
Is there a way to make it crash log?

If the server is actually crashing, you should have crash dump files in your server's install location. If not, it's likely not a crash.

where is crash dump file? 

Sorry for the delay, the "crash dump" would be where RustDedicated.exe is located generally. Some hosts do shutdown for high memory usage, that wouldn't be a crash.