Motor is sluggish, Necchi Model#4795

Question

The motor runs but is so sluggish/slow that sewing is impossible. It's a sudden problem that my neighbor also has -- same machine, bought on the same day, but mine lasted about 6 months longer. About 2-3 years old.

Janome 4900QC six months old. Today, on turning machine on, it is sewing very, very slowly despite attempts to vary speed with slider. I woyuld really appreciate some help.