Sounds like there is an issue with either SSL settings, otherwise you’ve misconfigured something with a redirect rule/workers/pages?
May I ask which instructions or steps have you followed trying to achieve the redirect from one domain to another using Cloudflare dashboard?
Furthermore, if the “old domain” is using Cloudflare, you could achieve this by pointing the A www and/or A olddomain.com to the temporary IP address like 192.0.2.1 with proxied status, therefrom followed by the tutorials to make a redirect from one domain to another via Redirect Rules.
I used the steps which i do normally like adding nameservers in domain settings
then pasting A @ (domain name) record.
third thing the CNAME but the issue is I don’t have hosting what should I place there like in the IP address?