I've been suffering from vibrating issues since a long time, but finally its solved now.
I'll just give a summary, might help you!
btw get your suspensions checked.
my cultus vibrated a bit at low speed but then, while gaining speed it got stable
but after 100 it vibrated like hell, everything shook.
As led by mechanics, i got my suspension and steering bushes, boots etc changed and re-done from a "kharaadia".
but it was now use. (Still get them checked in your case)
Anyways, later a mechanic finally diagnosed the problem. The car had alloy rims, made in karachi and adding fuel to fire, those rims were altered and did not set perfectly, which was dangerous too. I changed the rims and now have original cultus steel rims.
another issue which is not noticeable at the moment, the tyres are re-done too and are not very smooth and leveled. get them checked from a tyre wala too.