Help with (sometimes) slow site

I have had zen cart running for a few days and most of the time the speed is fine, but occationally it slows down to 30 to 100 sec/page for a few seconds or minutes. Then it goes back to normal. It is a share host. We have tried moving to a different mySQL server. The programs and images are on one server, and the mySQL database is on another server (is this usual?)

Here is the site http://yarntree.com/cross-stitch/

Here is the parse log http://yarntree.com/cross-stitch/temp/page_parse_time.log

Here is a copy of the server info http://yarntree.com/cross-stitch/temp/serverview.mht

Any help or suggestions would be most appreciated. Thanks.

This can happen on sites that are on overloaded servers or servers that are not optimized for php and MySQL ...

Currently your site is fast ...

If this is happening on:
Shopping Cart to Checkout
Login to Checkout
Checkout Link
Shipping Estimator

then you could have a shipping module with issues such as UPS or USPS where the server for the real quotes is not responding for 30 to 90 and sometimes 180 seconds ...

Right now you have an odd shipping module reading:
Shipping Cost Will Be Calculated At Shipping

So I don't know if you turned off your shipping or are using something else ...

Check with your hostings site if this continues to be an intermittent problem or you notice that your server is rebooted often ...