2003 Camry LE vibrating gas pedal

[aagii]

I bought a brand new 2003 LE last month and have put
2300 miles on it. Now whenever the car gets hot,
say after half an hour of driving, I can feel high frequency
vibrations on the gas pedal in the 10-40mi/hr range. This
vibration goes away when the speed getts higher, e.g.,
in the highway. Does anyone here have the similar
problem or know the reason for it? Thanks!