One of my cats is about 1.5 years and has tremors/ muscle spasms
when he sleeps. When I got him he was ~7 weeks old and had been
rescued from a railyard. At first I thought it was a kitten thing
combined with dreams of the rough time he had in the rail yard. (his
mother had died over a week before he was caught)

Unfortunately the spasms have continued. They're not violent and are
limited to his legs. They also don't seem to bother him or wake him
up. I've also never noticed them while was awake. In all other ways
he's healthy, active. I meant to ask the vet but unfortunatly he had
other problems when I brought him for his shots and yearly physical
and I forgot.

Is this something I need to be worried about in the short term? Or
is he just having dreams involving running, jumping, etc. The other
cat I have has some interesting dreams which include meowing and
occasionally growling, hissing and spitting. I asked the vet about it
and was told that he was healthy and was just dreaming. Since I toss
and turn and occasionally talk in my sleep it made sense.