Dog limping on and off for weeks, sometimes having trouble getting up

Our dog has been limping intermittently on her front legs for about four weeks — sometimes on the left, sometimes on the right. The pain on either side seems to be worst while putting her paw on the floor. The lameness is especially bad in the morning and improves throughout the day. The pain mainly occurs when she tries to get up, especially when pushing herself up with her front legs. Especially her lower body will shiver during these periods. She has periods of one to two days where she is completely free of symptoms. No limping, no pain, no crying. But sometimes the symptoms suddenly start getting worse in the afternoon and peak at night. During these "pain phases" she has trouble standing up. She will often cry, sometimes even scream. It is worth noting maybe, that she doesn't really seem to take pressure of the legs outside of "pain peaks". Even when she is slightly limping. She will jump up the couch like it doesn't bother her. Something she doesn't do much anymore is using the front legs to stretch. And on the rare occassion when she does it, she will scream when she stretches too deeply. Also we haven't done a prolonged walk in these four weeks and always take the elevator instead of taking the stairs.

We went to the normal vet a few times. She did a bloodwork which was good and we had X-rays taken, which show no bone problems. Gabapentin and Onsior did not bring any noticeable improvement. After that we went to an orthopedist who physically examined the neck and checked her movements. A cervical disc problem was ruled to be unlikely but not impossible. The neck was movable to both directions without any pain. She is a shiba so she was overly dramatic during the check-up. She wouldn't really let him conduct the motor function tests. Also on that day the symptoms were almost unnoticable.

I'm really at a loss. The orthopedist told us to just wait a little longer. But the cycle seems to stay the same: two days of almost no symptoms to no symptoms and then usually one day of intense pain and limping. The next step would be a MRT check-up, but that would cost around 2.000€ where we live, which is not trivial. I would be endlessly thankful for advice.