Other than that, mostly it's just fears about methods of dying. I would hate to be buried alive. IMO, one of the worst ways to die.
Dying by asphyxiation is not so bad. Let me tell you about it.
Once my friend and i had a challenge. We wanted to see who could swim the longest underwater. We figured 2 pool length ie 60m x 2 will more than adequate to determine the winner. So we started from the shallow end, thinking that when on the way back we ran out of breath, we would only have to stand up as we will be in the shallows.
We prepared ourselves by hyperventilating to the point of almost losing consciousness.
Then taking the last big breath and holding it, we kicked off from the shallow end.
We reached the deep end. No problems; easy peasy. We kicked off from the deep end - still underwater. He was always just ahead of me. OMG! we reached the shallow end and still have enough breath. We kicked off the shallow end. He was still slightly ahead of me. I don't want to lose out to him. My chest start hurting. Then my lungs seems to be on fire and felt like bursting. Pain peaked to white hot.
Then suddenly the pain reduced and was gone. My peripheral vision - the black borders of which grew wider and wider. My vision was tunneling smaller and smaller. The black borders had stars twinkling. It was getting harder to hold on to consciousness. I knew that if i go on any longer, i would lose consciousness and drown. Now i know why when autopsy is done - some drowned people have no water in their lungs. At last, i reached the end of the deep end of the pool, reached to top and pulled my head to air and breathe.
With that episode, fear of dying by asphyxiation is now gone forever.