Nervous laughter is a physical response to misperception, stress, tautness, or anxiety. Like sweaty palms or an elevated heart-rate. It's not something you intentionally choose to do. Nervous laughter has nothing to do with your sense of humour, and can overcome you at the unfunniest of moments. and generally the most embarrassing times too.
Wait... why do you always laugh?
Anyone can be caught off-guard and discover themselves laughing inappropriately at something that everyone else is taking seriously. But when it becomes a customary response it becomes more than a one-off aberration that you can safely ignore. It can get in your way socially and professionally, and leave you feeling uncomfortably insecure about yourself.
What can be done to overcome a tendency to inappropriate laughter?
How to help yourself
The first thing is to take a good look at the sorts of conditions that set you off. Is it always with certain people or friends? Maybe when you feel required to 'perform' in a specific way? Are there occurrences when you know it definitely won’t happen? What's different about those times?
When you begin to think about the matter in this way, you can stop just cataloguing yourself as 'a giggler', and begin to make some selections about shifting the way you contemplate about (and respond to) difficult events. You may want to look at ways of enhancing your self-confidence, or you may contemplate changing how you interact with the persons who appear to initiate you.