My Website Sometimes shows unexpected Hosting's Default Coming Soon Page

I'm having this problem since 10 days ago , my website suddenly showed Coming soon page with a message " if you are the site owner please login to launch this site , if you are a visitor . Check back soon " , although my website was live .
Coming Soon Page: https://i.imgur.com/AgrnqUN.png

please help what stuff should I check to see if there is something wrong with the website settings , the url to the website is http://www.bellusclinics.com

I looked into the DNS settings and noticed that the domain is not pointing to the hosting ip address , so i fixed it and the website worked , but now sometimes i open the url of the website and see this coming soon page again after couple of minutes when i refresh the page the website shows up. notice: i have cleared the cash and cookies in my browser but with no luck