Dodge Intrepid

I have a 1995 Dodge Intrepid. The problem is intermitten but very troublesome when it happens. When I turn on the car or occassionally while I am driving, the guages (tach, speedometer, indicator light, heat guage) will stop working and the car will not shift out of low gear. I had it in a garage twice and each time they did something (tighten a ground wire and something with the computer). The problem is still happening. Sometimes it snaps out of it within a few blocks, sometimes it takes considerably longer (7 or 8 miles). Any help as to what this is or what I can do will be greatly appreciated! Thank you!