It started 2 weeks ago and i thought it's from some bug on one of my wp templates, but then 2 days ago i went to one non-wordpress site, which is my own csm, without any javascripts, and nothing external used in it. It happens 2 of 10 times i open the site: I type url, press enter website starts to load normally and BOOM white screen and in status bar i see "transfering data from load.s3.amazonaws.com" and this lasts infinite I thought this could be a virus or something... but it happens only on my websites. I have over 30 domains on 4 different hosts and it happens on all of them, no matter of cms of whatever. I apologize for my bad english i hope you can understand me.
That may be caused from few reason, Have you asked your hosting company to investigate the problem? In case you need more help send me url for one of your website that has this problem and some online way to contact you such as skype, messenger. Good luck!
You mentioned you have sites with different hosting companies and that all you're sites seems to be doing this regardless of what cms they use? this sounds like a jacking script or cookie on you're computer itself. what you can try and do is scan you're computer with superantispyware and malwarebytes.delete any infections found reboot computer and check to see if the problem still persist. Alternatively you can check the .htaccess file to see if it has that link in it. if it does remove it clear you're browsers cache and reload the page check to see if its still redirecting to that site.
If you have Amazon Affiliates codes across your site and there is broken Link somewhere I have seen this happen in the past, if not then I'm afraid I don't know - ask your hosting company.