Parse Time: 0.290 - Number of Queries: 86 - Query Time: 0.0766816908112
Parse Time: 0.288 - Number of Queries: 100 - Query Time: 0.0687398138275
Parse Time: 0.690 - Number of Queries: 193 - Query Time: 0.116967580963 (on a product)
Parse Time: 0.759 - Number of Queries: 209 - Query Time: 0.0983346674042
Parse Time: 0.508 - Number of Queries: 136 - Query Time: 0.0810130088196
Parse Time: 0.290 - Number of Queries: 78 - Query Time: 0.0510682418518
Parse Time: 2.124 - Number of Queries: 513 - Query Time: 0.719797956299 (All Products page)
Parse Time: 13.075 - Number of Queries: 513 - Query Time: 7.31642122157 (All products, page 2)
Parse Time: 10.349 - Number of Queries: 513 - Query Time: 5.16953373636 (All products, page 3)
Parse Time: 1.330 - Number of Queries: 513 - Query Time: 0.268626236816 (All products, page 4)
Parse Time: 1.457 - Number of Queries: 513 - Query Time: 0.303080993423 (All products, page 5)
Parse Time: 4.504 - Number of Queries: 213 - Query Time: 1.54430867732 (on a product)
Parse Time: 14.750 - Number of Queries: 192 - Query Time: 4.7538081226 (add second item to cart)
Parse Time: 0.762 - Number of Queries: 215 - Query Time: 0.108870370667 (on a product)
Parse Time: 6.278 - Number of Queries: 249 - Query Time: 2.98983435551 (add 3rd item to cart)
Parse Time: 11.335 - Number of Queries: 261 - Query Time: 4.33027916937 (specials page)
Parse Time: 0.463 - Number of Queries: 81 - Query Time: 0.0602936174622
Parse Time: 0.242 - Number of Queries: 81 - Query Time: 0.0635035597534
For the most part, your slow responses appear to be occurring when the database is responding slowly.
Some other times the page is slow to process likely due to the large size of the content on the page.
Other times it's slow while the server processes the data received back from the database.
The slower times can be frustrating, but I suspect it's mostly a result of the busy-ness of the server you're sharing with hundreds of other hosting accounts whose sites are busy doing other things at the same time as you and your customers are trying to shop.
There's not much you can do about the intermittent slowdowns, other than move to a server that's tuned more efficiently and is loaded with fewer other customers.
You may pay slightly more for hosting if there are fewer customers sharing the same server ... but you should experience fewer bottlenecks vs what you have right now.