can you hear the disk spinning? if it sounds bad mechanically there's a good chance the fan isn't running properly
other than that my first recommendation would be to try the drive in another machine, cuz it could well be a broken controller. if it is the drive then your only options are pretty dire (if you can't afford to have it repaired professionally). try tapping it firmly (but not so it breaks) with your knuckles. try putting it in the freezer for about an hour, this may allow it to work for another 30-40 minutes, enough time to back up important data
if none of this works then i guess you'll have to open it up, but this is definitely a last resort and it's highly unlikely you'll be able to fix it. before resorting to this i would recommend waiting a few days, repeating the tapping/freezing and trying again (this has worked for me, obviously it doesn't make much sense but it probably makes more sense than opening your disk). don't touch the surface of the disk with your hands and don't do it in a dusty room. power the disk while it's open and if it doesn't spin, try giving it a push start. check for any damaged bearings, if you find one use a tiny bit of oil on it. and the absolute last resort is to swap the motor assembly with that from another identical drive. i've tried doing that twice and it hasn't worked yet, so good luck
