Facing 503 service temporarily nginx unavailable

Hello, I am currently experiencing a problem with my website servers being down in the last few days. This has happened multiple times throughout the day and is affecting three websites, including my own. These websites are: https://tm-speedtest.com/ and https://kalkulator-spalania.pl/ As a result, the user experience on my site has been compromised. I would appreciate some guidance on whether this issue is related to my hosting or Cloudflare. Thank you.