This is normal. Apache web server does it to keep it's threads alive that are waiting to accept new connections.
But as a rule of thumb to prevent unnecessary risks make sure you don't have all the modules enabled by default. Only enable modules that you need. Also I see that you are using apache 2.2 probably you should use the latest one 2.4.9 if you can update.
You can also run some tests on your server that checks some basic vulnerabilities like one provided by SSL labs
There are more commercial products available from Qualys and Nessus that can run scans.