What of the log entries just prior to the SIGTERM line? Yes, am aware that if I do /sbin/service httpd restart I will see SIGTERM, but that's system admin restarting the service manually. Question, I guess, should have been, is there some event which is causing a restart of the apache server?
Does it come backup after restart cleanly ... no errors? Or does it fail to restart and then attempts yet another restart until it builds that digest?
I too have been running Moodles since 1.4 and do know that some work needed to be done with DB when upgrading. I take it that all those have been done as one upgraded over the years. What of the health check in Moodle?
These snaps of logs - which should be watched in realtime in this case - are somewhat helpful, but none (other than yourself) can see/determine if any entry in the log is significant.
Might I suggest installing Mutitail?
http://www.vanheusden.com/multitail/
When having issues, nice to be able to see multiple logs on one screen. Have a script (watchweb) where root user can call up five related Apache logs and watch in realtime - the access_log, the ssl_access_log, the error_log, the ssl_error_log, and the rewrite.log. If I run that in one terminal session window and then in another terminal session window do a /sbin/service httpd restart can SEE what's happening.
'spirit of sharing', Ken