1991 Chevy Caprice front brakes hanging up

Hi, for the first few miles everything seems fine, then the front brakes start to drag. After a while sometimes the front end begins to shake. Between 40 and 60 mph.
not all the time. The guy that works on the car checked out the front end and nothing seems loose. The tires were taken off and balanced so that is good. New shock were installed. Still does the same thing. I'm thinking the anti lock brakes are making it shake. Can one disable the anti lock system because I have heard it is really expensive to fix something like this.