What Causes Choking Even On Saliva?

I am choking more these past few months. So much that a friend suggested I see a doctor. I am near the heimlich method. I had to have it performed on me maybe 4 years ago. It seems I am choking on saliva? It causes me social embarrasment. But mainly it causes fear in me that I am going to die from it. Is It serious? Denise H.