My cars shaking in fifth gear why?

Hello Im having some automotive troubles. Just the other day my car started shaking ever time I shift to 5th gear. If im doing about 62mph+ the shaking is gone but at lower speeds in the gear it shakes tremendously. I can ride 4th till about 55 mph no problem but as soon as I put it in 5th gear a strong "wobble or shake" occurs. BTW I am driving a 1993 Ford Escort if that helps anyone. Thanks in advance!