As the condition is ongoing you definitely need to discuss with a doctor. If your primary care doctor, check first to see if he/she can do an electrocardiogram.
Remember have the details of your symptoms down accurately, and when they started, how often they happen and if there is anything you can relate... from your note there seem there is no cause-effect I can guess at.
I had just turned the sprinkler on in my front yard and it started. I get real lighted headed and then the pressure starts in my neck and my heart rate goes crazy...I have woken up at night doing this and I was driving down the street about 3 weeks ago and it started.
See a doctor.
You heart rate should never be higher than about 150, and then only if your are doing something physical, like walking up several flights of stairs or walking briskly up a grade (hill) for example. I give these numbers for an average 60 year old, and that applies only if your are normal weight and can pass a medical physical exam with no corrective actions recommended.
Has this happened only once? If yes, what was the cause, were you frightened or running.... ?