The feeling of hot or cold is actually just the feeling of heat energy entering/leaving your skin.

The basics: if something is cold, energy is moving from your hand into the cold thing. If something is hot, energy is moving into your hand from the hot thing.

If it cannot transfer energy at all, then it doesn’t feel hot or cold. Like when you take a shower at the perfect temperature where the water temp matches your skin exactly, and it doesn’t feel like anything. Or a very warm pool.

Your hand would overheat a little bit eventually because your body creates internal energy through being alive, which it radiates away through your skin to the surrounding air to maintain equilibrium. If your hand lost that ability, it would get a bit warmer internally. But your blood would maintain approximate temperature equilibrium, so it wouldn’t be too bad.

If you were in a pool of the stuff, you’d eventually cook yourself.

Source: got a physics degree a bunch of years ago and kinda remember some things. But I’m not 100% confident of any of this

What you're describing is a perfect thermal insulator.

What does it feel like when you're wrapped in blankets? You feel warm, despite the blankets generating no heat of their own. They do this by insulating you from the outside temperature.

It would feel like being wrapped in a warm blanket, and if you were fully submerged, you'd end up overheating as we're constantly generating heat that we need to get rid of.

Like putting it in liquid that is at exactly your body temperature.

I can only partially answer this. Humans cannot sense moisture on the skin, only temperature and tactile (e.g. something on the skin, or moving along the skin like a droplet)

Something that cannot transfer heat would, I assume, feel not like putting a hand in water, but rather something....else?

Answered in other comments, just to not spam my answer.

I would assume you'd feel the temperature, though your hand would not change the liquids temperature. Think about walking into a hot room, you feel the heat.

If you were drifting through the vacuum of space without a spacesuit, would you not freeze? Not sure if this comparison works though.

Okay, this is my undocumented, your average Joe type of guess, but here goes: as there is no heat exchange with its environment, I assume your hand would burn from its own heat.

I would assume you'd feel the temperature, though your hand would not change the liquids temperature. Think about walking into a hot room, you feel the heat.

If you were drifting through the vacuum of space without a spacesuit, would you not freeze? Not sure if this comparison works though.

I would assume you'd feel the temperature, though your hand would not change the liquids temperature. Think about walking into a hot room, you feel the heat.

If you were drifting through the vacuum of space without a spacesuit, would you not freeze? Not sure if this comparison works though.

I would assume you'd feel the temperature, though your hand would not change the liquids temperature. Think about walking into a hot room, you feel the heat.

If you were drifting through the vacuum of space without a spacesuit, would you not freeze? Not sure if this comparison works though.

I would assume you'd feel the temperature, though your hand would not change the liquids temperature. Think about walking into a hot room, you feel the heat.

If you were drifting through the vacuum of space without a spacesuit, would you not freeze? Not sure if this comparison works though.

I would assume you'd feel the temperature, though your hand would not change the liquids temperature. Think about walking into a hot room, you feel the heat.

If you were drifting through the vacuum of space without a spacesuit, would you not freeze? Not sure if this comparison works though.

I would assume you'd feel the temperature, though your hand would not change the liquids temperature. Think about walking into a hot room, you feel the heat.

If you were drifting through the vacuum of space without a spacesuit, would you not freeze? Not sure if this comparison works though.