Who would you say this? Sunflower seeds are salty for no reason... why would you ask this question? Say something like this on Google, and don't tell people to shut up of shut the hell up, you can get hated for a reason so just... report the question and never think about it, just get some confidence in you at least
TOO much salt can kill you. There are unsalted sunflower seeds and salted so no they can't kill you. You'd die if you for some strange reason decided to swallow lots and lots of salt. Eating one of those sunflower seed packages won't.
I don't know why sunflower seeds are salty, but I'd guess that salt is a side product of one (or many) of the metabolic reactions in the plant itself.
Salt can only kill you in high concentrations, but the same goes for anything you eat. Too much of something is always bad. Drink too much water, for example, and you'll die. You just have to be moderate in what you eat. If you eat sunflower seeds, try to eat other foods with them that have a low salt concentration.