The Squid just wants you to know that you aren't alone. We too, have had similar feelings at some time or another. We cannot say if it's a phase or not, but we did get over it. It may be linked to some mild depression, or you could simply be curious. Just make sure you keep these curiosities just that... Curiosities.
Edit: P.S. If you are curious about death, a good book that is very stimulating in that department is "Sum" by David Eagleman. Try it out, it's a good read, and perhaps if you explore this topic a bit, you will be able to move onto another, (perhaps more happy) one?