Find out where it is coming from. Get a frequency analyzer... it could just be sensitivity to something like a smart meter. If someone is beaming shit at you, then it's probably very high frequency... Mhz-Ghz, so it can't really penetrate that well. If it is high energy x-rays, you need something like lead or tungsten, but x-rays don't bounce around a lot, so it has to be in a focused beam from some direction, so just build something that masks your head, onto the back of your chair, wrapping around. If it is radio waves or something lower energy, you might be able to just put foil on your walls.
It all depends on the frequency used, but you need a freq analyzer to determine that... BUT, as a catch-all against any BROADCAST signals that use resonance rather than directed high energy stimulation for effects... find a closet. Line it is heavy duty aluminum foil, all the way around. Make sure and get the doors and use conductive tape on the seals and hinges, and you're set.
If it is coming from above, it is probably directed from a drone or beamed from satellite. Since it is directional, you can line the roof of your office, but you'll need something pretty potent, like a mm of lead sheet... maybe 2.