2002 mazda proteget vibrates when in reverse idles fine fine in drive

Check the transmission fluid with the engine at operating temp and idling to make sure it's not low.If the vehicle has any type of mechanical linkage at the transmission, make sure it's connected properly and in the correct orientation.

This sounds like the torque convertor. It usually will idle fine and when shifted cut out and die. Its like a manual shift and you let the clutch out to fast or didnt have enough rpm's. if you are in the middle of accelrating it should do it alot less. mostly when letting off the gas. You may want to check the nsbu switch also its the nuetral safety back up switch. it usually keeps your from starting but may kill your engine if there is a short.
Your car is new enough, that when put on a (good ) scanner it could show a code to the issue.

Check the air intake hose for tears or rips as the MAF sensor will miss the extra air coming in a tear that opens with car in Drive flexing the air intake hose .

You have a broken part inside the transmission, it will need to be torn down and inspected.

Possible dirty throttle valve and idle speed control valve.

Throttle Body Cleaning on vehicles without electronic throttle control (most 2003 and down)

You can in most cases repair this slow speed stall or unstable idle by cleaning the engine throttle valve and the idle speed control valve using a product called CRC Spray Throttle valve cleaner. Spray the cleaner into the air intake of the engine with the hose removed from the throttle body, the engine will try to stall so hold up the idle speed manually. Once you have used up about 1/2 can of the cleaner stall the engine out while spraying and turn the key off, disconnect the negative battery cable for 5 minutes and then reconnect and drive the car for a about 25 miles of varied driving modes. If this doesn't cure the problem you may need the fuel injectors professionally cleaned by the dealer service dept.

if what your feeling is not an engine miss,
then it will be a motor mount,best chances are the front center one,,
or top trans mount

check the motor motor mounts for movement,
watch how far engine rocks forward or back with it running and foot on brake

check serpentine belt tenssioner

hello,good day,seem you have problem on ignition or fuel system,maybe one spark plug or nozzle need replacement,or better to send your car to a dealer for proper diagnose,ty

hi barry i have the same problem did you ever fix yours ?