If I had to die, I would go out by sleeping preferably.
That I think is the easiest, painless way to die. Any painless and easier way?
Just because you are sleeping doesn't mean you feel no pain. If your death is a result of a heart attack during sleep you will feel the pain, will likely awake in pain, and if the attack is acute enough you will die in pain. Then when found it will look like you 'died in your sleep'.