Здравствуйте!
При загрузке главной страницы вашего сайта идет огромное количество подобных запросов к MySQL:
[pid 23749] 15:54:40 poll([{fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 1471228928) = 1 ([{fd=7, revents=POLLIN}])
[pid 23749] 15:54:40 recvfrom(7, «1 1133 23def 5total f? 25 10201 5 3376 2 3 4 02315 5376 2 », 1719, MSG_DONTWAIT, NULL, NULL) = 61
[pid 23749] 15:54:40 sendto(7, «3201 3SELECT COUNT(DISTINCT p.product_id) AS total FROM oc_category_path cp LEFT JOIN oc_product_to_category p2c ON (cp.category_id = p2c.category_id) LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id) LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = „1“ AND p.status = „1“ AND p.date_available <= NOW() AND p2s.store_id = „0“ AND cp.path_id = „130“», 468, MSG_DONTWAIT, NULL, 0) = 468
[pid 23749] 15:54:40 poll([{fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 1471228928) = 1 ([{fd=7, revents=POLLIN}])
[pid 23749] 15:54:40 recvfrom(7, «1 1133 23def 5total f? 25 10201 5 3376 2 3 4 02565 5376 2 », 1658, MSG_DONTWAIT, NULL, NULL) = 61
[pid 23749] 15:54:40 sendto(7, «3201 3SELECT COUNT(DISTINCT p.product_id) AS total FROM oc_category_path cp LEFT JOIN oc_product_to_category p2c ON (cp.category_id = p2c.category_id) LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id) LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = „1“ AND p.status = „1“ AND p.date_available <= NOW() AND p2s.store_id = „0“ AND cp.path_id = „217“», 468, MSG_DONTWAIT, NULL, 0) = 468
[pid 23749] 15:54:40 poll([{fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 1471228928) = 1 ([{fd=7, revents=POLLIN}])
[pid 23749] 15:54:40 recvfrom(7, «1 1133 23def 5total f? 25 10201 5 3376 2 2 4 0115 5376 2 », 1597, MSG_DONTWAIT, NULL, NULL) = 60
[pid 23749] 15:54:40 sendto(7, «3171 3SELECT COUNT(DISTINCT p.product_id) AS total FROM oc_category_path cp LEFT JOIN oc_product_to_category p2c ON (cp.category_id = p2c.category_id) LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id) LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = „1“ AND p.status = „1“ AND p.date_available <= NOW() AND p2s.store_id = „0“ AND cp.path_id = „62“», 467, MSG_DONTWAIT, NULL, 0) = 467
[pid 23749] 15:54:40 poll([{fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 1471228928) = 1 ([{fd=7, revents=POLLIN}])
[pid 23749] 15:54:41 recvfrom(7, «1 1133 23def 5total f? 25 10201 5 3376 2 3 4 02395 5376 2 », 1537, MSG_DONTWAIT, NULL, NULL) = 61
[pid 23749] 15:54:41 sendto(7, «3201 3SELECT COUNT(DISTINCT p.product_id) AS total FROM oc_category_path cp LEFT JOIN oc_product_to_category p2c ON (cp.category_id = p2c.category_id) LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id) LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = „1“ AND p.status = „1“ AND p.date_available <= NOW() AND p2s.store_id = „0“ AND cp.path_id = „112“», 468, MSG_DONTWAIT, NULL, 0) = 468
[pid 23749] 15:54:41 poll([{fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 1471228928) = 1 ([{fd=7, revents=POLLIN}])
[pid 23749] 15:54:41 recvfrom(7, «1 1133 23def 5total f? 25 10201 5 3376 2 3 4 02355 5376 2 », 1476, MSG_DONTWAIT, NULL, NULL) = 61
[pid 23749] 15:54:41 sendto(7, «3201 3SELECT COUNT(DISTINCT p.product_id) AS total FROM oc_category_path cp LEFT JOIN oc_product_to_category p2c ON (cp.category_id = p2c.category_id) LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id) LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = „1“ AND p.status = „1“ AND p.date_available <= NOW() AND p2s.store_id = „0“ AND cp.path_id = „265“», 468, MSG_DONTWAIT, NULL, 0) = 468
[pid 23749] 15:54:41 poll([{fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 1471228928) = 1 ([{fd=7, revents=POLLIN}])
[pid 23749] 15:54:41 recvfrom(7, «1 1133 23def 5total f? 25 10201 5 3376 2 2 4 0165 5376 2 », 1415, MSG_DONTWAIT, NULL, NULL) = 60
[pid 23749] 15:54:41 sendto(7, «3201 3SELECT COUNT(DISTINCT p.product_id) AS total FROM oc_category_path cp LEFT JOIN oc_product_to_category p2c ON (cp.category_id = p2c.category_id) LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id) LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = „1“ AND p.status = „1“ AND p.date_available <= NOW() AND p2s.store_id = „0“ AND cp.path_id = „348“», 468, MSG_DONTWAIT, NULL, 0) = 468
[pid 23749] 15:54:41 poll([{fd=7, events=POLLIN|POLLERR|POLLHUP}], 1, 1471228928) = 1 ([{fd=7, revents=POLLIN}])
[pid 23749] 15:54:41 recvfrom(7, «1 1133 23def 5total f? 25 10201 5 3376 2 3 4 02225 5376 2 », 1355, MSG_DONTWAIT, NULL, NULL) = 61
[pid 23749] 15:54:41 sendto(7, «3201 3SELECT COUNT(DISTINCT p.product_id) AS total FROM oc_category_path cp LEFT JOIN oc_product_to_category p2c ON (cp.category_id = p2c.category_id) LEFT JOIN oc_product p ON (p2c.product_id = p.product_id) LEFT JOIN oc_product_description pd ON (p.product_id = pd.product_id) LEFT JOIN oc_product_to_store p2s ON (p.product_id = p2s.product_id) WHERE pd.language_id = „1“ AND p.status = „1“ AND p.date_available <= NOW() AND p2s.store_id = „0“ AND cp.path_id = „131“», 468, MSG_DONTWAIT, NULL, 0) = 468
Складывается ощущение, что при загрузке главной подгружаются все существующие на сайте товары и не по одному разу. Еще заметили, что блок категории при загрузке сразу выпадает - http://i.imgur.com/G2RLP1P.png , вероятно эти две проблемы связанны.