I went to bed in my base with 20+ villagers in the room next door. There was a villager linked up to my bed, so an iron golem spawned in there. When I went into the sleeping position though, the golem became hostile and started attacking me when I stood up. I killed the golem, but it confused me why it became hostile.

Another instance of this is when I killed another golem that had spawned. When I went to pick up the ingots, the other golem started attacking me.