Electric seat jerks in small steps rather than moving smoothly

A mechanic checked the track and said it was clean. The seat sounds as though it’s jerking along a gear, one gear at a time. Any ideas? Thanks.

The seat slides on the track, and clean is good, but the gears that drive the seat may be worn, dirty, or broken, which could cause the symptoms you describe. I believe further inspection is needed, and I’d imagine the seat will have to be removed to access the drive mechanism.

Many power seats transmit the power from their seat motors via cables that look like speedometer cables,these cables coulds be damaged,the sockets for the cables can be damaged,you could have a motor failure,or the motor could be falling off its mount

You should have stated yr/make/model. Recently I have seen publications from GM stating if this happens on a new car the slide assembly needs to be burnished. To do this have a person about 200lbs. sit n the seat and operate it fully back and forth about 30 times.
Hope this helps.