Have things been normal since coming back home? If so, it might just have been a temporary thing, or maybe the beginnings of an age thing that's accentuated at altitude, but you might want to keep an eye on it. Was the shaking from the cold unusual for you? Maybe you just meant it was cold, but if that's not your normal reaction to night temps, it could possibly mean something infectious (bladder/kidney infection, prostatitis). If it's anything that worries you, might be best to get a medical exam to set your mind at ease (don't want to mess around with your kidneys!).

Since you only report this the first 3 nights, I'm guessing it might just have been a temporary thing and nothing to worry about. Maybe guys in your age group can weigh in on this...