This is more than likely a startup program not responding.
Try reducing the startup programs:
Start/Run and type MSCONFIG and select startup,now untick everything except your AV and Firewall,also leave any realtime Antispyware program ticked.Now reboot.
This will not cure the problem as we do not know what exactly is causing the problem.
Though you could try disabling one at a time from MSCONFIG and reboot to identify the culprit.