What are the reasons for frequent nightmares? I can't move or shout, and I'm in a cold sweat.

The first possibility is physical weakness; Most people have nightmares when they have a cold and fever, but not frequently.

The second possibility, the influence of evil spirits, is commonly known as ghost pressing bed. Does anyone in your family often burn incense and worship Buddha, or do you like astrology and often tell fortune? In fact, this is not good, which shows that you have opened a window in the spiritual world, and evil spirits can easily rule and intimidate you. I have experienced this situation before, and then I became a Christian in 2007, so I hardly had nightmares. Not afraid of anything. If you are in this situation, I suggest you go to the church for help and find a priest.