I have a Western Digital external that does that some times — three clicks, then it spins down and plays dead. What happens is that the drive runs really, really hot, and it either shuts down thermally, or the connectors work loose due to the heat expansion and contraction. I’ve modified the case so I can slip it off to cool, and so that I can reseat the connectors. Usually, once the connectors are reseated, it runs fine — for a while.