For something quick, suggest using terminal and viewing 'top'. It could be, as already suggested, that the DB server on the same server is struggling to keep pace with the 'traffic'.
Also check the config of apache ...
# prefork MPM
# StartServers: number of server processes to start
? running # worker MPM?
As far as a dedicated server for DB, may not be a bad idea. One can dedicate nearly all the memory of that DB server to nothing but DB, thus, also, allowing increasing apache servers on the web server box, etc..
No 'quick fix' without investigating the whole system.
'spirit of sharing', Ken