Today my server was ok, up and kicking without problems but them, some hours letter when I was going to take a look at some domains, the apache test page was showing up for every hosted domains/subdomains in that server.

To make everything to work again I just restart every service.

Since the only person who have access to this server is me, it's incredible strange, what logs could I take a look to see what have hapening ?

Regards,
LDKS

try apache logs...