Hi again,
I have purged the cache for autoptimize, cloudflare and the browsers but the problem is solved for Chrome and Firefox except for IE.
I have followed the instructions on a previous thread on how to find the culprit and it seems that the Genesis Simple Share plugin is the issue. I have disabled it and it seems to be solved, except for IE. Sometimes I get that blank page for a split second and it turns back to normal.
Out of topic, but do you have alternatives to displaying social share buttons that dont consume too much site speed?