You need to remove encryption from your private key file like this:
openssl rsa -in server.key -out server.key.new
mv server.key.new server.key
Make sure the new key file is only readable by root – otherwise anyone with shell access to this server will be able to grab the private key and impersonate your server.
To make the key readable only by root, do ‘chmod 600 server.key.new’ before swapping keys.
Now you should have Httpd Apache2 automatically started without SSL Passphrase prompt.