There might be many reasons for the slowness and it's hard to tell what particular reason it might be in your case.

If you're using the default Zend file cache, the first thing to do is empty your /files/cache folder.

After this, you should check your caching settings. This can be done through c5 dashboard System & Settings => Cache & Speed Settings. Then you might also want to switch over to more robust caching framework, such as APC which uses RAM instead of individual file system files which makes it many times faster. Here's something about APC (there is also a link in the thread on how to install it on your server if it's not installed):
http://www.concrete5.org/community/forums/chat/wow-5-4-apc-fast/...

One possibility is also 3rdparty blocks that you have on the slow pages. E.g. I had a site with the Mail Monkey block in the global footer which slowed every page down very much because it connected the API on each and every page load. I forked the block by adding caching to the API calls which was the key to success.

To debug this situation, I'd suggest to build a plain page with no blocks, not even header/footer blocks (or possible hard coded blocks in your templates). Then, one by one start adding the blocks and then see where the bottleneck is.

Here's some tips but each case is individual and hard to say the particular reason in this case. Hope this helps!

Best,
Antti / Mainio

Sometimes, the cache system can slow down your site. This happened to me on a server with slow I/O but more or less fast MySQL.

In the screen Antti mentioned, try to disable the cache.

Oh and just because it's slow on a different server doesn't mean it's not the server. Especially with these cheap mass hosting companies you'll sometimes have some performance issue...

concrete5 definitely requires more server power than a static HTML site but it runs okay on a vast number of server.

Have you used C5 before? If so, did it run smoothly?

If not: C5 does need a bit more power than some other CMS in my experience. Some shared hosting services just don't match up to that. This doesn't mean you have to get premium hosting, it means you should pick a host that uses up to date hardware and does not put too many accounts on one machine. Often the big guys (like Strato) don't offer a good performance at all. In Germany I can vouch for this. My sites running on Strato took about 25 secs to load a page. Now they are with another, cheaper host and load in seconds.