Stopping fights before they start

I find I am consistently triggering combat unintentionally. I walk into the wrong building, boom, ambush. Press a dialog option that makes sense, swords drawn. Exploring a boss lair with another character while my tav is in dialogue, don’t touch anything or the minions are on-sight.

My open world gaming experience was from assassin’s creed a long time ago, and it’s fun, but is this a common experience? I’m still new to dnd as a whole, and the consequences of meandering around has me quick saving all the time in case I walk into a cult ritual or a boss battle by mistake.

Any tips mechanically for reducing that experience?