Wireless and bluetooth share the same card
You can try running the Diagnostic/AHT http://support.apple.com/kb/HT1509
However, not definitive by any means, but may kick out an error code.
Can you test by changing to Ethernet cable?
To trouble shoot further you can:
Try a SafeBoot https://support.apple.com/en-us/HT201262
Takes noticeable longer to get to the login screen, does a 5 minute disk repair before it loads up, and certain system caches, dynamic loader cache, etc. get cleared and rebuilt.
This test will tell you if third party interference; extensions etc are not loaded in safe boot mode.
Test issue in another user (or guest user) account https://support.apple.com/en-us/HT204443
This will tell you if it a universal issue or isolated to your user/admin account.
I would double check your >Preferences>Energy Saver
—changing "wake for network access"
—that you do not have some "Scheduled " preferences that got triggered.
Watchdog daemon helps restart the server if its operating system becomes unresponsive (a "hang"). On computers that support automatic restart, this option can be activated in the Energy Saver pane of System Preferences. Once activated, Watchdog periodically resets the computer's Power Management Unit (PMU) timer. If this timer expires (which happens if the system hangs), the PMU forces a restart. ref:macos - MacBook Pro going to sleep by itself because of watchdog daemon - Ask Different