Did you update to Big Sur? Are you using something like Little Snitch or TripMode or any other network filtering extension?
When it crashes, it it a full macOS Kernel Panic that requires a reboot?
If so, see this thread:
There was a complicated compatibility problem in the public release of Big Sur. Apple changed how network extensions work. If any were active, and the Plex DLNA server started, the OS crashed.
A quick solution is to disable the DLNA server. Some network agent providers have updated their apps. And the Big Sur 11.1 beta resolves the issue, too.
