Losing my religion, and shikantaza I was raised in a secular family, went to CofE church a little as a young child, but only to support my mum. Actually I'm way more drawn to Nietzsche now than Christianity, though I cannot see any answers in his work.

I visited Thailand as a teenager, took a few meditation classes, and would say I had a sort of conversion experience upon reading more about Buddhism, in general. But don't feel like there's any reason to keep my faith; it hasn't I think helped my mental health or my life, only got me to where I am today. Almost spiritually exhausted.

In effect, I feel like I have nothing to look forward to and nothing to look back at. I am scared of dying, but not to the extent that I would assume a religion to cheer myself up.

For a long time I believed that I won't be annihilated when I die, but the more I think about it, and I have done so a lot, the more it seems that this is an irrelevance, something that tells me about my life now not the future.

But, I can sometimes feel good in the present moment, and wondered whether shikantaza might help me feel better about that. I can't find an exact phrase to describe that, but maybe Soto zen might help me to be how I am or want to be, in life and death, even though I am so tired with everything but this fluctuating enjoyment of now. Which incidentally, does not seem very Nietzschean: I don't place much value on happiness as a way of life hedonism etc.

I have visited a local Soto group, without meeting a teacher there, and enjoyed doing so. The people seemed cool etc., too. But I wanted to ask if Soto meditation has the answers to the rest of my post, or what the answers were. Even what I am asking.

Thank you for any encouragement or for any insight.
Shikantaza means "just sitting" or "single-minded sitting". It is a state of being where you are present here and now, no matter on what you experience, in body or mind.

About losing your religion: the Buddha said that there are three marks of existence, one of them is impermanence of all compound things (anicca). In other words, anything that once begins to exist, one day ends (changes to other thing or ceases to exist). So your opinion about what is your religion, or even yourself and what you consider your religion, will certainly change and/or cease to exist.

About your annihilation when you die: one of main questions that buddhism bring to us is this: "What is this I?"? Because most of times we get identified with things that we bring with us, like the body that we carry or the thoughts and emotions that we have. We think that these things are "me", however, these also are compound things that began one day and that will cease to exist certainly. If you strip yourself of all impermanent things in yourself, what remains? Is there something that remains? So what is this that you call "I"? Before answering to where will you go when you die, you must answer what is this that you call "I" and answer what in this "I" dies with the death of the body.

Zen buddhism have quite diverse opinions about where are one going when s/he dies. Each master say one thing, but for certainly, the most important thing (and that's what shikantaza and enlightenment is all about) is to be totally in the present moment. This does not means that it's wrong to make plans for the future: on the contrary, it means that even making plans, you are totally conscious that you are in the present moment, and any plan may not happen, and even knowing that you are fine.

Suffering (dukkha) for buddhism is also inherent in all compound things, because when they cease to exist, if one haves desire or attachment for it, s/he will suffer. Buddhism says that there is a root, a cause for desire or attachment to exist, that is a kind of ignorance, a delusion, that prevent one of experiencing the reality as it really is. And that's what about shikantaza: experiencing the reality as it is, completely, here and now.