Check to see if the LF brake rotor is discolored, like black or blue,(compare it to the RF rotor). Possibly the brake caliper is seizing up OR LF brake hose to caliper failing internally. If you can get it to happen when you're on a back road with no traffic around, (like 10 MPH max. I would never try this at highway speeds), whip the steering wheel back and forth while maintaining steering control,no foot on he brake pedal. If it frees up I'd say the caliper is seizing up. If not I'd go with the hose. If so I'd change both LF and RF brake hoses. They're a lot cheaper.