Friends of mine diagnosed with depressive disorders have described sensations such as these. To reiterate what our colleagues have said, make sure and get checked out.

On a more personal note, I think I recognize that odd feeling, it comes over me every once in a while 5-20 minutes at a time or even an hour or so if I'm home alone with not a lot to distract me. Though, I don't believe I will be any help in giving advice on how to dispel these feelings as I don't resist them, though I admit they are unpleasant.

I take it as a chance to tap into an unusual perspective. In this state of mind it's easier to conceptualize ideas that are beyond reach otherwise. Why do people reject one another? What is the point of continuing to live your life the same way you've been doing it all along? What do you REALLY want right now and what is standing in the way? Where is the human race headed and what do you have to offer to make its destination better? Why do you do things that you regret and how to you keep from doing the same stupid thing again? If something is not right, this depressing but truthful feeling of disconnection can be the cure, if you use it mindfully.