Do you eat a lot of tuna fish, or restaurant sushi? These contain mercury. See
this post. You can also be exposed to mercury if a mercury thermometer gets broken in the home, and the mercury is not cleaned up (it can then evaporate as mercury vapor, which is breathed in). Very old electrical equipment can contain mercury tilt switches, which if broken in the home can lead to the same problem.
Have you considered the Doctor's Data hair analysis test for mercury? If you want to detox, then the Cutler protocol seems to be the one that people tend to use.
Your symptoms might be due to some other reason though. Although it is considered an alternative health diagnosis, one thing worth considering is pyroluria. This supposedly can give people a nervous disposition. You can be tested for pyroluria, but it can be easier to try the treatment for pyroluria, which is vitamin B6 and zinc, and see if that reduces nervousness.