The problem started just after the installation. When I logged in for the first time to admin page of my WordPress website it went to the usuall dashboard for only 1 second and then the only thing I could see was a white loading page. To change anything I had to manually type posts page's adress to be able to move around admin pages. The problem occurs at bashboard, occasionally during typing a new post and when I try to input any wigdet into header, footer, etc.
The same thing happens on 2 different websites on 1 hosting server. Plugins and themes are not the problem, as the problem starded just after WP installation.
I am rather inexperienced WP user so please let me know what more info should I provide.