Since I was like 12 I was blessed with the genetics of an 80 yo. Having muscle spasms, hernias, and all sorts of bizarre crap. The two times in my life I got into a workout regime things would get progressively better until months down the line, when I'd have to do surgery of some kind, likely because I 'worked out too much'. Doctors tell me to start lifting weights, but they don't seem to believe me and simply tell me I'm a male and young and shouldn't be as frail as I am. No tests in 20+ years have shown anything out of the ordinary, except for whatever problem I developed all of a sudden, so it's no wonder. I'm afraid that trainers in a gym wouldn't be any better. Got no idea where to start. Pool workouts with the elderly maybe?
Use resistance bands. No weights to drop on yourself and even bodyweight can be dangerous if your body drops
That's the safest strength training I can think of