I have 4 different Isekai stories that I'm working on (not all published.) I try to make their method of death something that references the plot you're about to see on the other side in miniature.
In "A New Hero God," I have the protagonist who is a child psychologist die by taking a bullet for the student he was counseling. He gets reincarnated into a super-hero world where he becomes the leader of his own super hero team, with the special "Hero" and "Sacrifice" abilities which enhance his abilities when he's placing himself in danger to rescue someone else with the power enhancement proportionate to the level of risk to his life he is under.
In "Key to the Void," the protagonist gets tempted by a demon to make a deal for his own life and soul in order to heal his granddaughter. This turns out to be a MASSIVE chunk of the plot of the story on the other side told in miniature as they in the other world will be repeatedly strung along by a demon who attacks and threatens their loved ones in order to manipulate them step by step down a dark path.
In "Hell's Underworld," the protagonist dies in the exact same car wreck that paralyzed Key to the Void protagonist's granddaughter. It is a parallel story to "Key to the Void." His method of death involves him driving home with his friend and friend's little sister. He's the driver, they are blaring really loud music and he's driving distracted. The story turns into a redemption tale in which he's figured out if he's reincarnated then his friend and friend's little sister are probably reincarnated as well and wants to find them and apologize.
In "The Class of Outworlders," the protagonist is a soldier who dies in the literal battle of Armageddon. Or rather, "Har-Megido" as it was originally pronounced in Hebrew, which translates to "Hill of Megido." It's a literal place in the real world, located in current day Israel, and is known as the bloodiest battlefield in all of history due to it's high strategic value in the region and the fact it's become a major battlefield in every major campaign in the middle east before the modern day. But, in this case, it actually is also the one that takes place in the Apocolypse. He then gets reincarnated after the battle of Megido after God has cast out all the demons, and the demons from Earth are now invading another innocent world that he got reincarnated on and he has to help defend them from the very forces that got him killed in his first life.
So, those are some ideas from things I've done. It does help your story a lot to somehow connect the death with the story to come in some kind of symbolic fashion. For this to happen, you should have a pretty good idea of what your plot is actually going to look like on the other side in the first place. I can also name a good few well known anime adapted Isekai that have one the same, Overlord and Mushoku Tensei being the prime examples.
