(I am not a medical professional, and you should consult a doctor for your medical advice.)
For a while, I suffered from reduced sensation along the outside of my forearm, extending to the fourth and fifth fingers. These regions are serviced by the ulnar nerve; this condition is called ulnar nerve entrapment. These symptoms can be straightforwardly resolved by building muscle to cushion the ulnar nerve.
The ulnar nerve is same as the “funny bone” nerve on the elbow, which can be struck directly to induce an uncomfortable tingling sensation.
Ulnar nerve entrapment happens because the ulnar nerve is compressed as it travels past the elbow. If you think of your nerve as a string running along the outside of your arm, it’s clear to see that bending your elbow would cause it to become taut, and therefore experience more pressure at the joint. Therefore, you could expect that keeping your elbow bent for long periods of time would make you more susceptible to ulnar nerve entrapment.
At night, I would often develop a pins-and-needles sensation of numbness along the same region on my arm. Eventually, it got severe enough that it started waking me up regularly. I purchased elbow pads (such as these) to wear at night, which helped, but didn’t address the root cause.
I solved this issue more permanently by building the appropriate arm muscle, which somehow cushioned the region. The triceps muscle is a set of three muscles on the back side of the arm. In particular, the medial head of the triceps is located just above the elbow. By strengthening this muscle, my problems went away — and when failing to maintain this muscle, they come back.
Since I am very weak, I found success with lying triceps extensions using 10- or 15-pound dumbbells. After a few days of regularly exercising my triceps, I stopped being woken up at night due to tingling in my arms.
An alternative is triceps push-ups, which can be done without equipment. However, it can be to execute these with good form as a beginner.