make sure you 12volt power supply is good, then check your  V-Ref the stepper drivers

+1 and maybe check the connection from the PSU to the board.  If you have the printerboard with the barrel connector check that connector along with where it is soldered to the board.

tried reducing the speed but no change, still the beep. It feels as if motors are trying to move but cant. I tried without any load. Still all they do is make long beep.
When I send M119 i get following response
>>>m119
SENDING:M119
x_min:L y_min:L z_min:L

what i have noticed is, if i give move command repeatedly 8-9 times, the motors make usual beep noise but then move for like 5-6 revolutions.
its like, beeeeeeeeeeeeeeeeeeeeeeeeeeeeeeppp....then the move and halt
next time if i give only give move command once, they only beep.
REgarding endstops: as i said i tried giving commands more number of time, during beep if i press the end stop, the motors stop making the noise.
Some times what happened is motors would continue to make noise, even if i disconnect prontoface. Its only after i kill power that they stop. if i turn the power back on in like 1 min, the same motor would still be making noise.
Sometimes the motors also grunt.

Please help