Please note the following is my belief. I do not believe anything can possess a person. What about those that channel? The person is allowing that spirt to work with them as a tool and there for even if they may not remember what they have said or what they have written down. There higher self or a guide is still protecting them during this process, and the spirit is allow to leave afterwards. If the person experience habits and traits that aren't there's, and may be from an ancestors or another spirit.
Then they have a choice whether they wish to keep it as their trait or not. The same goes for possession. If a person fights hard enough and ask for protection for help on whoever they believe and have trust. Then that possess will fade because that spirt does not have a right to be in that person body.
Anywho moving on to your question and ignoring my little rant. I personally think that they can't astral protection in that state. Protection takes up a lot of energy and if your holding something that isn't yours. Then your too drained to even try and attempt astral protection. Again it may also come back to how experience they are. If they are some form of pro at it. Then it might be as easy as climbing a step, but if they had only recently started it. Then it might be like climbing a cliff.
Would it be like sleeping? I don't think so. It would most likely feel like you don't have control over your body.
Either way make sure with what your dealing with is not a medical issues. Not everything has to be a being possessing you. If you have anything negative and you don't work with that energy in your craft. Banish it. Only you have a right to your body at the end of the day. It's why you were born with it.
The reason I ask is because I have lately been experiencing signs of demonic Possession and it got me thinking about a dream that I had a few years ago because the dream felt like a warning at the time. In the dream I think I found myself dead and was trying to get back into my own body. When I made contact with myself in my dream I felt such a cold electric like shock that I jolted me awake. Might be just a strange dream that I’m over thinking but it doesn’t seem that way. I guess you are right that it might be mental issues but it really doesn’t feel that way. I definitely would rather be wacko than possessed. Anyway thank you for listening because that dream has been on my mind for years
Not allways. Depending on how deep within the person the invading entity is, they might be oblivious to it. The wive of a mentor of mine was lightly possessed by Belial ( I think) for two years before noticing anything strange. If it‘s just piggy backing a few bad dreams and occasional blackouts might be all you get.
