I'm at a very different moment in life than you are, but several years ago I had a severe panic attack "out of the blue" while managing a large project. Once I'd understood what was going on, I responded like a good little geek and checked out the research on panic attacks.
While you should definitely seek the help of a professional, as you can dangerously misdiagnose yourself, the most likely cause is a high level of stress that you haven't been managing. Anxiety disorders in general become progressively harder to treat the longer you live with them, so don't try to just tough this out.
If you need it, a psychiatrist may be able to prescribe medication which can provide short term relief. Far more effective over the long term will be to engage in some cognitive therapy and learn to recognize the early symptoms that you are not managing stress and respond to them before your stress results in anxiety.
I would recommend the site www.anxieties.com as a good place to start. It's run by a respected clinician in the field, and while the site advertises plenty of materials you could pay for, it has a fair amount of information and advice available for free.
The good news is that if you take this seriously, respond quickly, and learn to comprehensively manage your stress, then your odds of avoiding a chronic anxiety disorder are quite good.