My 1998 Honda civic LX break light randomly comes on and off while driving. Any ideas?

Question

Yes, the ebrake is down.

Yes, the ebrake does work.

Answer 1

check the brake fluid its low

Answer 2

that usually means your braking system has pressure that is a bit low. Check/add brake fluid if needed and then check the system for leaks. Also maybe there is something touching the switch for the ebrake which is usually just a little button that is pressed by the ebrake when its engaged, and bouncing around makes it push it from time to time. That happened to me once

Answer 3

Your brake light is triggered by a switch right above your brake pedal underneath the dashboard.  It is also triggered by another switch under your ebrake.

By a Honda Civic Service manual if you don't already have one to learn where these switches and screws are so that you can inspect them carefully for loose connections or locknuts.  Replace the switches if their faulty.

Good luck!