Been there many times, seen that many times. My customers always
complained of a transmission shudder. If you haven't done a tune-up in a
long while, then change the plugs and wires, then go from there. Ignition
misfires usually happen under a load. Part throttle at cruising speed. If
you lay into the throttle, the misfire goes away. Plugs and wires installed
by you, are the cheapest fix.
A dishonest mechanic will sell you a trans first, and then tell you that
you need spark plugs and wires.
Last week, a friend of mine, asked me to check his daughter's '95 Grand
Am. It had a misfire, and a check engine light. The mechanic he took the car
to said, "You need 2 fuel injectors, spark plugs, and wires", ($600). I told
him to change the plugs and wires. Grand Am's didn't have many fuel
injection problems, for that year.
He changed the ignition components ($60). I reset the "check engine"
light, and like magic, all his troubles were gone.
You could still have a misfire, due to a bad coil. But, if those plugs
and wires are old, change them first.