I have a 2000 Cherokee sport 4.0 I was driving on the highway and my tac and speedometer went to zero for a few seconds and back to normal none of my other gauges changed it repeated a few times trying to figure out what it could be

 

Vehicle Speed Sensor on the way out?

 

I would guess it's a electrical problem in the dash.

 

did you touch the ignition key? happened to me the other day when i accidentally hit my key.

 

My 98 does the same thing at times. It in a common problem with them. More then likely the connection behind the instrument cluster are loose or dirty. You will have to pull the cluster and clean them and add some dialectic grease to the connections. That should take care of your problem.