Suicidality is an exceptional case with common root. It is common for parts of someone's subconscious to perceive risk or danger and manifest those perceptions into motivations that are not in line with that person's conscious intention. This is where hesitation comes from as well as all self-sabotaging behavior. Self-sabotage can be subtle and I imagine it is more common than we believe.
When these subconscious parts go dark enough they can lead to death in the form of suicide. Like their minor cousin hesitation, they are often misaligned with that person's conscious intentions.
Answering "am I suicidal?" is complicated. Answering the question "do I want to die?" is impossible. Because to qualify them you have to ask things like, "does any of me want to die?" or "does all of me want to die". And those questions may never be completely true or false. But I feel strongly that if your reading this, you are inquisitive, and that means part of you wants to live. That part is enough if you utilize it.
If you are presently experiencing suicidality and you are not in the care of a psychoanalyst or psychiatrist, please seek professional help. Suicidality has been understood by medical professionals for long enough that treatment has a relatively high success rate.
That being said the ER is your best friend if you are in crisis. Think of it as a shitty hotel where they take your temperature every morning.