You can turn on devel mysql log to see if you which queries are taking too long. You can also turn on the mysql slow query log in your mysql `my.cnf` file. Once you do you can see  which query is taking too long, you can move on to optimizing it.    
I suspect you are using views for this page. If that's the case, check the views filters. Try to add proper filtering on index columns from the node table. Or any other index column. In addition to that, check to see you have mysql cache enabled.