Sounds like a product defect or a virus/rootkit/malware infection. My bet is Dell will have you perform a factory restore so my advice is to prepare for that. Be sure you have backups (more than one) of what you can't lose prior to the call to Dell.
Remember I can't guess if you have things plugged into the USB ports.
Restart or startup is not working on first attempt to startup
Laptop hangs at the Dell logo, dell logo flashes and the screen is black with light on. Push the power button than windows will load normally. This is an ongoing problem I have refreshed system 5 times and this corrects the restart issue. System is stable and startup and restart will work normally. After a couple of weeks startup and restart will not work properly. Dell diagnostics all passed. Computer is up to date with all updates. This is Windows 8