Last night was scary. I woke up at 4:30 laying on my back, with little feeling in (of all places) my left arm, and having a hard time breathing. -___- I stayed up for two hours looking up heart attack and stroke symptoms. Eventually I read something that said the history of 20 year olds having heart attacks without pre-existing conditions were next to zero, so I went back to sleep. Woke up, left arm was fine again. I think it was related to some nerve issues I was having a couple months ago that made my pinky go numb... Either way, not a fan.
Of course that was scary, and you were right to check it out. But I've had that happen, and your medical advice is almost certainly right -- you don't need to worry (at least about the arm issue).
It may not even be "nerve issues," just circulation getting cut off temporarily. I am quite prone to my feet and legs falling asleep. And once, when I was using a sleeping bag during a Model U.N. field trip, my left arm fell asleep when it was under me. I half-woke and had a nasty shock -- not just that I couldn't feel my
own arm, but it felt as if
someone else's arm was in the bag with me!
As far as the hand numbness, since you're in a line of work that'll probably require heavy keyboard use over the years, hopefully you're getting good advice about ergonomics, hand position, etc.
When I was at SAP, I had the pinky and ring fingers of my left hand go numb for a few months. It was diagnosed as "ulnar tunnel syndrome" (counterpart of the more common "carpal tunnel syndrome"). Luckily, my responsible German employer bent over backwards to accommodate me -- a thorough evaluation by an ergonomics expert, advice on changing my posture, a special wrist-rest, rebuilding my desk chair, etc. Eventually, the problem went away. But it sure made me appreciate having all 10 working fingers again!