Am I stroking it in my sleep?

Your body is paralyzed for the most of the time you sleep so that you don't physically act out your dreams, so probably not.

Only one way to find out. Cock cage.

Could be.

There are plenty of people that do masturbate in their sleep, and it's more common during puberty.

However, most wet dreams are generated without manual stimulation. Typically, it's a combination of the stimulation of the genitals against clothing, or bedding with the brain's ability to process those signals into something else and match it up with whatever dreams are ongoing.

In some cases, it doesn't even need any physical stimulation at all. The brain can do all the work, so just the bare minimum stimulation from the aroused genitals just being there is all it takes to generate orgasm.

The pumping of blood, minor muscle tension and movements are all it takes when the brain is doing its thing.

Matter of fact, it's possible to have a hands free orgasm while awake for the same reason, though it takes practice.

wet dreams typically just happen.

but, eh, you might also be rubbing it out if you're not quite fully asleep. a lot of weird stuff can happen between waking and sleep.

Typically, automatically. But, you might be an outlier.