What is the suggested treatment and expected progression for lumbar radiculopathy? What did your neurologist say about the expected prognosis of this condition?
I know nothing about radiculopathies but if there is a treatment and you would respond to it you may be able to rule out ME if your reaction to physical exertion goes away because of this treatment. If you do suspect your symptoms might be because of ME you are not missing out on treatment for the time being, but it is probably a good idea to try to not go over your limits. You know, so you do not trigger that strong fatigue after doing stuff, if that is somehow possible.
If you are in Germany there is not much the medical system has for ME patients (to be very direct, it is probably a good idea to never mention to any neurologist that you suspect ME.), but if you want to rule out other stuff, in my personal experience the university clinics are often years ahead of average doctors.
I do have problems with coordination (gets worse with increased pain) and occasionally weird muscle twitching that may or may not be like the fasciculations you speak of, but that does not help much with the question of where your problems come from because the cause could be different. If you want you can try to describe what you feel after doing physical things, or just try to see for yourself if your experience matches the
Post-exertional malaise described from the link Mattie posted.
Don't be shy to ask anything that is on your mind, we may not have all the answers but maybe someone at least has an idea to point you in the right direction or something like that.