He's not quite sure where he is. He's not quite sure what he is.
He's not in his physical body. Okay, that's unusual, but not unheard of. He must be in some part of the Astral Dimension very far from the Material, because he can't see anything that resembles physical surroundings. Thanos must have used some pretty powerful magic to knock him this far out of his body—I guess they don't call them Infinity Stones for nothing—but Thanos had left Titan—
Oh wait.
He's dead. Big purple bastard must have completed his quest. Then he remembers. Big purple bastard had to complete his quest. They have one chance in 14,000,605. This isn't part of what he remembered of the one successful timeline.
He doesn't suppose it would be. The Time Stone wasn't showing him his subjective experience in the possible futures, more of an overhead view. He'd known he was going to die (and come back), but he had no idea what to expect in the interim. He hadn't really expected anything. For all of their arcane knowledge, the Masters of the Mystic Arts don't really have a tradition regarding an afterlife. He'd kind of always assumed he would just cease to exist.
What is this afterlife like?