Your question is actually a really interesting one because you are referring to a relatively rare phenomenon called hypnopompia (or, hypnopompic hallucinations, also sometimes referred to as hypnagogia). In essence, these are neurological "misfires" where the frontal lobe is not fully engaged until you have been awake for a few minutes. During the interim, there are a host of different symptoms the person may experience, including visions, paralysis, and garbled speech. They are harmless, although I hear loud and clear that you are quite upset by them - and understandably so, given the contents of the visions.
As a quick aside, there are theories that the hypnopompic/hypnagogic hallucinations may be responsible for alien abduction reports and lore, as many of the people who report being abducted also report a history of sleep disturbances. Not saying that you fall into this group, but an anecdote that you may find interesting.
As for stopping them, the main treatment recommendation for sufferers is to adjust sleep patterns to get more adequate sleep (these issues are common among narcoleptics - or, folks who tend to fall asleep spontaneously during the day). If you are particularly stressed out, anxious or depressed, you may be sleeping more poorly and therefore bringing on the condition. In other words, these may be less of a manifestation of your stress, and more of an indication of the poor sleep that is resulting from the stress.
In general, I recommend that you get the anxiety evaluated by a physician. A good talk therapist can also help you out, but perhaps a medication trial would work well to not only lower your ambient stress, but also help you sleep better at night and reduce the frequency and intensity of the sensory experiences you are having. I wish you the best! If you are satisfied with the response, please hit "Accept." That is the only way I receive credit for my answer. Thanks-