Strapi slow operation

I have a website (Next js + Strapi). Frontend located on a GitHub, backend - on Digital Ocean Droplet, images are stored at Cloudinary.

I noticed that if I do not open the site for a long time, for example, several hours, then it opens for a very long time. And vice versa. I think, that it’s because Strapi backend is “sleeping”. if there are no requests. What is the reason for this behavior? Is there any way to fix this?

The address of the website is:

Any suggestions are highly welcome.