Be aware that you can't always "see" a tripped breaker. The only way to be sure is to flip is positvely all the way to OFF position, then back to ON.
Also, I was tripped up once by an electric room heater that had a built in timer! The timer was turning it on and off per the default settings.
If these don't help, you should probably have an electrician check the cord, the receptacle, and the breaker.