ok mate... this is an issue with almost all Beltas (1000cc) & some Vitz...sad news is theres no 100% cure.. doing the following will reduce it.. but once this vibration starts happening it doesnt goes away .. trust me.. i have been 'fighting' this for the past 5 years
anyway.. you can do the following routines for "reducing" this idle vibration
regular throttle body cleansing/tuning/plugs cleansing (after every 2-3k km) & afterwards getting your RPMs reset thru computer
get your CAT (Jaali) cleaned (its at the front of the engine behind bumper.. it made a huge difference in performance once i got it cleaned last month..)
get the EFI (fuel injectors serviced)
change your CVT-TC transmission oil if you havent done so & the car has mileage of over 50k km. needs to be replaced after every 40-50 k
regularly add/mix HOBC whenever available/possible
you may add extra Earth to your engine.. its does slightly reduced this vibration in my case
& last..I have heard that changing engine is the final option (with 1300cc)