I am facing this problem too...........my solution is to stand it vertically...turn off your ps4....unplug the power cord....wait 2-3 minutes and turn it back on....Will solve the problem temporary as it might happen in the future....Happen twice to me already. Im guessing the eject button is quite sensitive that when the rubber feet at the bottom when hot will expend and make contact. This is suggested by other users in other forum when i tried searching for this problem

I think when the ps4 do not have any disc inside and you press the eject button the ps4 will beep 3 times.....i think its a firmware glitch or there is a design flaw with the eject button......i am not sure too.....