Well, if your server is fully managed server, then you should seek help from technical support dpt. of your web hosting provider but after reading your post I think you are using unmanaged server hosting. In this case you can take the risk of restarting server at the time when the traffic is very low. If your website is a business website them I would suggest you to inform your visitors in advance through a notification about prior unavailability.
You can also find some information over Dell BMC System at :- http://forums.host.co.in/showthread.php?t=...p=9173#post9173