Toshiba laptop keeps rebooting with no message at start up?

The laptop is a toshiba satelite c655 when I turn it on it comes up with the toshiba leading innovation logo then it goes to the black screen with the white line in the top left then after that it just crashes and comes back on and does this repeatedly it won't let me go to safe mode as I tried each function on the keyboard I have no repair ddisk either I believe this is froma virus but if it isn't what can I do to fix this.