Seen a different but related issue
Back in the days of Netware, diskless workstations and 10Base2 coax networking, I was a similar situation. Computers wouldn't boot up early in the morning, but by the time I in to take a look, everything was fine.
The end result was that there was a long coax under the building eaves, and the cabler hadn't vrimped the center pin properly. Overnight, the temperature dropped and the metal contracted enough to break the connection. Once the sun came up and warmed the cable, everything worked.