Yes, several ideas, but without more information from you, it's impossible to give any specific information.
How many plugins do you have? How complex is your theme? Are you including a lot of videos or images on your front page? Do you have a lot of disabled themes/plugins still installed? Are you on shared hosting or VPS? Which version of PHP are you using?
You haven't even included a link to the website in question. This is a bit like calling your doctor, telling him you don't feel well, and then asking for a prescription.