Hi KittyLady,

As bonbon1993 mentioned, anxiety/panic attacks can cause this to happen.

Forgetting to breath can happen to people who do not have a health issue. Example: When exercising the instructor will usually say "breath in, breath out." This is because sometime we can hold our breath without realizing it.

You might try focusing on your breathing and do breathing exercises. You may also want to check with your doctor for peace of mind