Some of it might be partially posture based due to using smaller devices.
Hunching shoulders, tilting head downward for extended times, locking elbows in to body Those postures can close down the area where a lot of our veins, arteries & nerves travel.

It's hard to set up a tablet or phone be very ergonomic.
But stretches & doing reverse postures at times can help offset the negatives.

You might check for head forward, shoulders forward postures and see if working on that makes a difference for you..

But there is EMFs to consider also.. EMF stands for electromagnetic field.
EMF Health Effects - Electromagnetic Field (EMF) Safety from Safe Space Protection

EMF - Google Search