This could be caused by wrongly selected SSL options in SSL/TLS tab at Cloudflare dashboard, usually the Flexible SSL option?
Therefore, it may be a sign that your origin host/server does not have a valid and a properly installed SSL certificate which covers your naked domain and www (and some other sub-domains too).
I am not familiar with 552, rather you mean on 525 error?
If so, kindly, to not repeat myself here again, may I suggest looking into the below post to find a solution for your issue which covers all the needed steps
