40yo m no weight-bearing exercise tolerance. i can do moderate cardio. when even light weights are attempted, i feel shaky and tense for days/weeks.

Bodyweight exercises: Rather than lifting weights per se, try bodyweight exercises. Check out http://www.mensfitness.com/training/build-muscle/15-best-bodyweight-exercises-men & http://www.muscleandfitness.com/workouts/workout-routines/5-best-bodyweight-training-exercises for some ideas. Don't forget to warm up before & cool down after to prevent excessive soreness & injury.