Apache server keeps crashing, "caught SIGTERM, shutting down"

SIGTERM is used to restart Apache (provided that it's setup in init to auto-restart): http://httpd.apache.org/docs/2.2/stopping.html

The entries you see in the logs are almost certainly there because your provider used SIGTERM for that purpose. If it's truly crashing, not even serving static content, then that sounds like some sort of a thread/connection exhaustion issue. Perhaps a DoS that holds connections open?

Should definitely be something for your provider to investigate.

I had mysterious SIGTERM shutdowns in our L.A.M.P. server, and it turned out to be an error in a custom PHP module, which was caused by mismatched versions. It was found by looking in the apache access/error logs at the time of malfunction. Don't forget to turn error logging on.

Have you asked your provider to investigate? I assume this is not a dedicated server,

On the face of it, this seems like a security exception and somone is trying to exploit it / or there is a process running at a set time which is causing this, can you think of anything that runs on the server every 2 days? Logging tools?

SIGTERM is the signal sent to a process to request its termination. The symbolic constant for SIGTERM is defined in the header file signal.h. Symbolic signal names are used because signal numbers can vary across platforms, however on the vast majority of systems, SIGTERM is signal #15.