Honda FIT ARIA: Vibration problem

[Abhie]

I have an HONDA FIT ARIA 2006 1.5L engine Manual Transmission. When I start the car in the morning there is a very noticeable vibration during idlying (1200- 1400 RPM), it reduces when I shift into 1st gear & start driving. the vibration dissapears after 10 - 15 minutes. This happens in the evening if the car is not used for around 10 - 11 hours. Kindly help with a solution.
PS:It is Not a VTEC engine.
Thanks