intermittent problems with dedicated server

I am experiencing some weird problems with my linux dedicated server, it is run with Direct Admin panel and Centos 5 64 bits. In the beginning It looked like my dedicated server was down, the problem is inttermitent, it's been happening for the last 3 days. All sites that are hosted in it were not responding. My sites have been acting very strangely for the last couple of days, sites were loading slowly, sometimes they did not load at all. This Sunday morning they loaded very slow, suddenly they stopped working, then again. Now they are not working but I received one email in my inbox while the sites were down. Sites are hosted with [login to view URL], a linux dedicated server with centos5 64 bits, IP [login to view URL] I am trying to ping my sites but they do not respond: [login to view URL] and [login to view URL] are two of those sites but if I try to ping the server's ip [login to view URL] or [login to view URL] I will get a response. I tried to reboot the server but I can't find that option at my OVH hosting provider, there should be a reboot option but the link is not where the help says it should be and I couldn't find anywhere in the backend. NOW they are responding, the problem is inttermitent :( It looks like the sites are working again :( So strange... They come and go :( What do you think could be the problem? I need to know about your experience before sharing access to the server and what you think the problem could be or the solution to it Looking to have an IT guy available for things like this (not only for this project), updating of the server, available all days of the week if there was an urgent thing (luckily they almost never happen).