Jenkins freezes my server periodically and randomly

Question

I have a web server running a website. Because I only have one server, I want to install Jenkins on it. I have followed the installing instruction from Jenkin's website, but the first problem I met is that when I start the service using sudo service jenkins start, it freezes the entire server for 30 seconds to 1 minute. Sometimes it freezes again after stopping the service.

Then, I followed the instructions for running Jenkins behind Apache. Even though my httpd is configured using HTTPS, I have to follow the "mod_proxy" instructions instead of the "mod_proxy with HTTPS" ones so I can access http://my-domain/jenkins However, it appears that my server periodically (and randomly!) freezes, making both the website and a direct server access impossible for about 1 minute (as when I start Jenkins' service).

The most important vars of my Jenkins config (in /etc/sysconfig/jenkins) are:

JENKINS_USER="jenkins"
JENKINS_JAVA_OPTIONS="-Djava.awt.headless=true"
JENKINS_PORT="8081"
JENKINS_LISTEN_ADDRESS="127.0.0.1"
JENKINS_HTTPS_PORT=""
JENKINS_HTTPS_KEYSTORE=""
JENKINS_HTTPS_LISTEN_ADDRESS=""
JENKINS_ARGS="--prefix=/jenkins"

Here is my httpd config (in /etc/httpd/sites-enabled):

ProxyPass         /jenkins  http://localhost:8081/jenkins nocanon
ProxyPassReverse  /jenkins  http://localhost:8081/jenkins
ProxyRequests     Off

# Local reverse proxy authorization override
# Most unix distribution deny proxy by default (ie /etc/apache2/mods-enabled/proxy.conf in Ubuntu)
<Proxy http://localhost:8081/jenkins*>
  Order deny,allow
  Allow from all
</Proxy>

NB: Please note that I am stuck with an httpd version 2.2.15 on a CentOS 6.4 server, so I cannot use the AllowEncodedSlashes NoDecode directive (it is available since httpd 2.2.18).

And here are the error Apache logs (ssl_error_log):

[Thu Nov 06 08:46:59 2014] [error] (111)Connection refused: proxy: HTTP: attempt to connect to 127.0.0.1:8080 (localhost) failed
[Thu Nov 06 08:46:59 2014] [error] ap_proxy_connect_backend disabling worker for (localhost)

I have searched over the web for solutions about the freezing problem, but I have found nothing.