DIAGNOSIS This indicates an intermittent electrical connection. The cause is usually a failing power button switch or loose internal wiring.
FIX Unplug the blender. Press and release the power button firmly 20-30 times. This can sometimes clean oxidized contacts inside the momentary switch. Plug back in and test.
IF THAT DIDN'T WORK The switch assembly is failing. The switch is integrated into the main control board inside the motor housing. The motor unit requires replacement.
HEADS UP A flickering light means the connection is unstable. The unit could stop working permanently at any moment or pose a short-circuit risk. Plan for a replacement.