This unfortunately is probably due to your host. I have several hundred Concrete websites deployed on many different hosts. Some respond very fast while others not so much. Concrete is a great object oriented platform but this makes it a bit resource intensive on certain platforms. For example Concrete, in my experience is terrible on Bluehost while responds quickly on Media Temple.

Thanks so much for your help. I contacted my host and they weren't really very helpful. Do you have any suggestions for hosts? thanks

Sorry. Just realized you already made some suggestions

Any shared host is going to be hit or miss (probably mostly miss at budget prices). I had some terrible experiences on MediaTemple's grid server and would recommend to avoid that (although others have praised the dedicated virtual tier). It depends partly on your expectations and the luck of what server you get put on.

I have had similar issues with my C5 website and am considering switching CMSs. My organization is low-budget and cannot afford anything better than shared hosting. In your experience what are some CMSs that do well even on a basic hosting plan? Our site is not complex, but I do rely on some basic modules, like forms and image galleries. I'm considering Joomla mainly because I'm already familiar with it, but I'm not sure about the relative performance of different CMSs. Any suggestions?

If its only when logged in, the culprit can often be an autonav set to expand too many levels through too many pages. When logged out, its all cached. When logged in, its worked out on every page.

Old page versions can also slow a site down, so run the core cleanup job repeatedly or extreme clean - but make a backup first, just in case.

Thanks for the ideas. I had actually already cleared old page versions. No improvements.
In number of pages, my site is tiny: about 15 pages across 2 levels, so I don't think the autonav would be affecting performance. But how might I set the autonav to not expand all pages?

webmaster55, you might also consider hard-coding your navigation into the html so you avoid the autonav block altogether. If your site really is simple that should be workable. Or as a test just remove the navigation entirely and see how the site loads. Then you'll know if the autonav was the culprit.

If your site is really simple then you probably don't need a workhorse like Concrete5 or any other "big" CMS to power it. If you're interested in switching you might look at a smaller CMS like Perch or a hosted CMS like Squarespace. All have pros and cons.

And of course, no CMS is going to overcome a slow host or unoptimized code and file structures, so you might look into where the bottlenecks really are (I have no idea, just throwing out possibilities).

I would be fine removing the autonav block if I were the one managing the site in the future. But I'll be passing on the management duties, and the site needs to be easily expandable for the next person. Otherwise...I'd be fine coding a CMS from scratch.

At this point, I'm leaning toward your suggestion of migrating to a different CMS (although we can't afford commercial ones like Perch). I'm thinking about Joomla, mainly because I'm familiar with it and past experience has shown it to run fine on even GoDaddy shared hosting. Any other ideas for free CMSs that run fine on low-budget hosting plans?

With that number of pages, I doubt very much if autonav overheads would be relevant. You could look at the number of page attributes in use. Lots of attributes for each page can slow things down.

Looking in a different direction, sometimes performance is more to do with how busy your are or who you are sharing the server with.

I use iPage for hosting and I feel that the site is very slow as well.
Not only on login but just visiting the site is pretty slow for my liking.

I use DreamHost with x2 concrete5 websites they respond very well :)