My 97 chevy s10 it shakes alot after they fix the heads

Take it back to them . no one can do their job , everyone's an asshole .

Most likely the spark plug wires are not put on correctly. But as others have said it's they're responsibility to fix it, not yours! You paid good money for a job to be done right! Hope that helps! Jim

Don't pay them to fix their mistakes!

check the harmonic balancer.