Search queries are slow

Hello, i am using visual+ theme from last weak, i have a website with medium traffic, last day i enable mysql slow query log for debug purpose and today log is full with slow queries, all slow queries are logged when the user search on site.

# Time: 150426  9:54:33
# Query_time: 1.064776  Lock_time: 0.000372 Rows_sent: 0  Rows_examined: 18816
SET timestamp=1430024073;
SELECT SQL_CALC_FOUND_ROWS  ***_posts.ID FROM ***_posts  WHERE 1=1  AND (((***_posts.post_title LIKE '%search_term%

and so on …

i am using mysql query cache, set to 64MB and using xcache for php and object+db cache set to 64MB’s
my DB engine is innodb.
any help will be extremely liked.
Thanks