Simple EEG circuit is not working
For reference and to protect against future edits, here is the schematic being discussed:



There are several issues:

Draw opamps like opamps!  This is very annoying to look at since I can't "see" the circuit without mentally deciphering the blocks.  I'm guessing the AD620 thing is some kind of amplifier, and I know a TL082 is.

There are no bypass capacitors on the power and ground inputs to the amplifiers.  There is no point getting into this any further until that is fixed.

Picking up tiny signals from the body requires careful analog design.  One problem is the huge common mode noise, since your body picks up stray signals from the environment.  You have to consider both pickup of radio stations, and capacitive pickup from nearby power wiring.

This is usually dealt with by having a reference electrode that the other signals are interpreted relative to.  For a EKG, for example, a connection to the right leg is typical for this.