1999 Suzuki Vitara vehicle engine revs increases but vehicl

I own this vehicle which has a 2.0L(J20A)engine,whilst driving this vehicle sometimes (not always)the vehicle seems to have disengaged from transmission and all of a sudden it gets connected again(the rev meter increaseas)then the vehicle runs normal again this problem is intermitant,when the O/D off light and the POWER button is switch ON(WHEN THE LIGHTS COMES ON IN THE DASH BOARD)We can see it blinking and that is the time vehicle does the problem.it seems that there is a link between the transmission and electrical I guess so.Even if both the power button is off and O/D on still same problem occurs.