Run a humidifier in the room. It is likely the room is very dry, which increases the occurrence of static electricity, including on sofas.
Spray the sofa with an anti-static spray designed for furniture. These are usually available where dusting sprays are sold.
Dampen a fabric softener sheet with water and rub the sofa with it to eliminate the static electricity. Repeat as necessary. You can also use a damp cloth, but the static will return more quickly.