Removed virtualbox-dkms, video driver changed from NVIDIA to Nouveau, installed kernel v 4.8.0-040800, three times performed cold boot (dmesg' outputs attached): boot times was much shorter, BUT dmesg still prints that "error -110".
Removed kernel 4.8 (not installed virtualbox-dkms, video driver still Nouveau): returned to previous state with long boot and errors in dmesg output.
Removed virtualbox-dkms, video driver changed from NVIDIA to Nouveau, installed kernel v 4.8.0-040800, three times performed cold boot (dmesg' outputs attached): boot times was much shorter, BUT dmesg still prints that "error -110".
Removed kernel 4.8 (not installed virtualbox-dkms, video driver still Nouveau): returned to previous state with long boot and errors in dmesg output.