That is such a dumb queston. There are way to many explanations. try reading a book about cars.
The brakes are the primary cause of stopping a car whilst driving.
Press the brakes or down shift
No. A bad starter would cause the car not to start.
What would cause my VW golf to cut out whist driving
There are many things that can cause a car to stall while driving it. If the plug wires, plugs or coils are bad and are causing the engine to misfire, the engine will run rough. This may also cause the car to stall when driving. Generally, it will start back up, but it may be difficult to keep the car running. If your car stalls while you are driving it, look for an obvious reason first. Check to make sure you have fuel in the tank. Do not sit there and crank the car over, trying to get it to start, as you will quickly wear down the battery if it's not already bad.
Several things can cause your car to cut off while driving. Run a computer check for possible bad codes to see what may show up as a cause.
see CarTalk.com
If the trye has gone out of round (an MOT failiure ) Yes the car will shudder when driving.
It is important to maintain speed while driving, unless coming to a stop. A car would decelerate if there was not enough fuel or electricity to keep the car running.
Yes, either can cause a shake while driving.
No.
cause yours is broken