Website taking from 30 sec to 3 minutes to load

I don’t know what’s causing the issue, but sometimes my website loads in 10 secconds, (thats the minimun) or even up to 3 minutes or so.

But now since yesterday its taking at least 3 minutes to load, and even up to 6 or 7 minutes…

The website url is: https://www.curiososdelpoder.com

I had installed wp-super cache but a friend recommended w3-total cache so i have that one installed. Sometimes the website gives me this error on Chrome: ERR_EMPTY_RESPONSE

Plugins installed and running:
Adrotate
Akismet
Custom Headers and Footers
ewww image optimizer
facebook comments plugin
nextgen facebook
si-contact form
social networks auto poster
timthumb vulnerability scanner
tinymce-advanced
w3-total cache
wp-custom-widget area
wp-smushit
wp-statistics
wp-megamenu