I'm using Appointment+ plugin. When you don't click any

Hello.

I'm using Appointment+ plugin. When you don't click any button (anywhere in the website) during at least 15 minutes, the next time you click (anywhere, frontend or backend) the page take too much time to response. Once the website response, everything is fast again. The URL is http://www.labarberia.eu

Any idea please?

Thank you.

Eduardo