Can bruxism cause a fit?

While bruxism is typically associated with stress, it may also be triggered by abnormal occlusion (the way the upper and lower teeth fit together), or crooked or missing teeth.

No.

It depends on what kind of "fit" it is. If it is a seizure the causes could be very different than someone getting emotionally upset and "pitching" or "throwing" a fit. There could be medical reasons...

Yes, it can definetly be a factor. Panic attacks during sleep, as well as general stress and anxiety, can cause grinding and clenching.

A person may do something like clench their teeth during a seizure, but epilepsy does not cause bruxism.