Website in not reachable on some ISPs [DNS_PROBE_FINISHED_NXDOMAIN] [ERR_NAME_NOT_RESOLVED]

It seems like from time to time my website has temporary problem with being reachable on some ISPs. It looks like website is reachable by typing its domain and 5 minutes later I am getting DNS_PROBE_FINISHED_NXDOMAIN/ERR_NAME_NOT_RESOLVED error, time later ok and again latter error and so on. If I use 4G/LTE - share mobile internet or just use a phone, everything works fine (problem never happened).

Many of my users have had the same experience (and their use a different ISP, hundreds of km away from others). That situation probably started months ago as I from time to time got information from my users about my website being unreachable, but I ignored these message as my website was working fine on my phone and didn’t get any mail from uptime robot.

From last 48 hours that trouble seriously increased as my ISP caught this illness and by increased numbers of messages from my users. I am using Cloudflare CDN, but I am not sure if it has caused this issue, as one subdomain which has Cloudflare DNS Mode only (no CDN only DNS server) is suffering the same problem. The domain with .cars ending.