Sounds like you dissociate. Sometimes, people who are depresed can get these wierd feelings also. I know I do when I am very stressed. I suspect that there are really a lot of people who do it. Sometimes one can get triggered by music, light changes, smells, or topics of conversation. You may not even know what it is that sets it off.
If it bothers you, take it up with your T, if you have one. It might help to concetrate on your breathing when it happens to bring you back to yourself. That might take some practice, though. It can be scary, but I don't hink that at this point, it's something you have to be afraid of. Huggs