Dear Hariharan Sekar, repeated scans of the same sample may give results, but becareful may be the Tg is located out of the scan range of temperature. My Regards

You can increase the resolution of your peak by increasing the ramp rate by which you perform the measurement.

See the following equation (term one is the differential heat flow, term two is the heat capacity, and the third term is the ramp rate)

dQ/dt = Cp * dT/dt

As you can see, the heat flow increases linearly with the ramp rate resulting in a more exaggerated glass transition.