If you have many SIGTERM and other services like exim, ftp also reboots without any logical reason, you can try disable cPanel or just cPanel TaskQueue Processing Daemon:

/usr/local/cpanel/etc/init/stopqueueprocd

then some magic:

mv /usr/local/cpanel/libexec/queueprocd /usr/local/cpanel/libexec/queueprocd___
mv /usr/local/cpanel/bin/servers_queue /usr/local/cpanel/bin/servers_queue___
mv /usr/local/cpanel/etc/init /usr/local/cpanel/etc/init___
mv /usr/local/cpanel/src/chkservd/chkserv.d/queueprocd /usr/local/cpanel/src/chkservd/chkserv.d/queueprocd___

then check:

cat /usr/local/apache/logs/error_log | grep shut