Apache and/or Mysql long latency on Linux VPS

I do not know where is the problem. It is so hard and confusing for me. I have a problem that I do not think you are inchoate, but if you have any suggestions I'm listening. I already have a server with 1.5 GB RAM and 2 GHz CPU. Every time I restart Apache or MySql the page loading become very fast, but after one or two request it loads very slow again Site is approximately 12 KB. i use johncms 4.4.0