I'm always reluctant to be that "RTFM" / "Did you try searching?" guy, but....
https://www.google.com/search?q=err_too_many_redirects+site:moodle.org
https://www.google.com/search?q=err_too_many_redirects+site:moodle.org
PS, did you try clearing your cookies, or even a different browser?