There are entire websites dedicated to how to shield your home -- or parts of it (office, bedroom, bed, etc.) from EMF and RF radiation.

I agree that some people are sensitive to this, and such shielding is worth it for these people. A greater number of people are affected in a *minor* way by this electronic "smog". It's good to turn off your WIFI router at night (at least) for example. And put your phones/tablets/laptops in "Airplane mode" when you can.

But you don't need to build an oscillator circuit, with a 555 Timer IC chip or any other way. I'm into electronics, so building circuits sounds fun and all, but you still don't need it in this case :)

You are making it unnecessarily complex. You need to paint your walls with a special RF shielding paint, seal your windows, etc.
You basically build a Faraday Cage of sorts around the area to be shielded -- you don't want to leave any gaps, if you want it to shield very well -- and then you ground that whole "cage" to earth. Which is just a simple matter of connecting the whole unit to a $14 copper rod driven into the ground. 

https://www.amazon.com/gp/product/B08MZ24MD4/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B08MZ24MD4&linkCode=as2&tag=httpwwwchanco-20 />

There are good websites going into detail on all this. You need to make your home into a safe haven from RF. Many have done this and reclaimed their health and ability to function in the process.