What causes the car to shudder when taking off from a stop?

if strigt gear possably clutch.

It sounds like you could use a tune up. Most cars needing new ignition components (ie: plugs, wires, cap, rotor, ignition coil etc.) will idle fine while at a stop. When under acceleration conditions the presence of dirty spark plugs, leaking or cracked ignition wires, cracked or carbon tracked distributor cap and or coil will cause this engine to miss fire. A trick I like use to finding ignition voltage loss is to run the car in a darkened driveway or street with the hood open and look for the electical arcs. Have a friend increase the rpms to about 3000 while you look, if there are leaks you will see them. Good Luck from Electroman!

These are both good possibilities. If the car is a manual I would definitely think this is a clutch issue. If automatic, I'd be inclinded to think that it's either fuel delivery or ignition components.

(To add to my previous post.) Depending on age and driving habits you would also be due for some engine/transmission mounts.