Remove the battery and AC charger, press the power button for about 1minute. Reinstall the battery and charger and power on again.
Do you have two RAM sticks installed? Remove one and try with only one. If this won´t work, exchange one stick with the removed one.
Reset the BIOS (this could void warranty if the device is still under warranty)
disassemble the notebook to remove the CMOS/BIOS batttery, wait for 10minutes and reassemble the battery and everything else. https/www.youtube.com/watch?v=9xax2-uafuw