Hello jacelove: I see this is your first post here on PC. Welcome to Psych Central.

I can't tell you what is causing your random suicidal feelings. I could, perhaps, offer some off-handed speculations. But, realistically, they would be nothing more than guesses on my part. And they would be as likely to be wrong as they are correct. (Perhaps other PC members will have some insights they'll wish to share.) However here are links to 2 articles, from Psych Central's archives, that may offer some possible clues as well as some suggestions regarding how to handle your suicidal thoughts:

How Suicidal Thoughts Can Become a Coping Mechanism

How to Survive Suicidal Thoughts

I hope you find PC to be of benefit.