I think it's important to warm up your hands and wrists with some very basic stretches for as little as 1-2 minutes before you touch the strings. As a "mature" beginner like yourself, I will vouch for this.

Open each hand as wide as it will go (repeat). Make a fist with each hand; repeat. Then make a fist and rotate each hand at the wrist, clockwise then counterclockwise. Finally, take each finger from your left hand, one at a time, and slowly press down with it on your right forearm; repeat with right hand and left forearm.

After you do that, the previous advice is good.