1). There are no errors explaining why this is happening
2). We have optimized the site twice already
3). We have implemented caching all around
4). We have done a variety of other things
Here is what we're planning to do
1). Upgrade to 1.5.9
2). If the upgrade doesn't we will use 3rd party assistance reviewing our databases
In case the 1.5.9 upgrade doesn't solve the issue, I'm looking for some recommendations on what we should do to try to find what is causing this. I assume one of them will be disable add ons 1 by 1. What other recommendations do you have?