My Arduino "forgets" a sketch after the turning power supply off.

So my Arduino UNO R3 Clone does not run the sketch that was uploaded to him after turning power supply off.
It just blinks the L led a few times,waits a bit,blinks again and it repeats.
For example I had the simple blink sketch that worked(it worked even after pressing the restart button),but I stopped working when I unplugged and plugged the USB.