Why do I get these panic attacks

[Thesamallard]

When I was younger I dealt with sleep terrors. For those who aren't familiar it's basically (correct me if I'm at all wrong) having extremely bad nightmares you can not fully wake up from. Typically when you do wake after the night terror you can not fully remember anything besides feeling fear. As I grew up they began to go away but I would experience panic attacks extremely often. I began tracking my eating habits, sleeping habits, and tried reducing stress. I now don't get them as often. However, I could be stress free lying in bed wth my eyes closed and I feel this heavy weight and fear that I'm almost in danger. I'm not fully having a panic attack, but it's like a pre-panic attack. I've found a way to calm myself and rid of the feeling but I am still so confused as to why I get it.

[Paxiled]

Don't know why, either.  Most people who suffer from chronic anxiety have no idea why they have it.  Some people can trace it to some traumatic or dramatic event in their lives, but most can't.  Science hasn't found a cause, either.  But one thing psychologist seems to agree on is that childhood fears aren't the same as adult anxiety.  One probably doesn't lead to the other.  

[SarahCummings]

If you've found the way to calm yourself, there's no need to torture your brain with trying to discover the reason why that happened in the first place. You should be grateful and proud of yourself for finding the way to cope with it. Not many people know how to achieve that. If you feed your brain with negative thoughts you can't expect to be happy, and I kinda got the impression that you are aware of that. So, once again, forget the past and focus on the present moment, that's my advice. I wish you all the best.