I've played Skyrim to mid 30s in the past, but it had been years.
Last night I received the quest in Whiterun to retrieve Nettlebane (The Blessing of Nature). It's held by a few spellcasters not far from Helgen. I showed up on the scene, sneaking. I found one of the spellcasters alone. I had Lydia with me. I attacked with my bow. The caster charged me, and I was dead literally a couple of seconds later. It was so fast I was shocked.
I'm only level 5. I don't use any mods that would give me items before I should have them, and don't want to.
Is there any way to determine, in game (no googling), which quests are too tough for my level?
Short of pre-googling every quest, or searching for them on YouTube, how do you play the game with reasonably few deaths?