97 bravada (need help)

when i start my bravada the temp guage goes all the way in about the first minute then the check guages light comes on then it will go back to where it is supposed to be and then sometimes do it a few more times.
any thoughts on what this could be?

also my brake light comes on and goes off from time to time. any thoughts on this would also be helpful.

If you're talking about the ABS light, it's likely a connection that makes and breaks and after so many successfull starts it'll reset. A diagnostic scan should trace it down during the alarm event.
I'm assuming that you mean the temperature guage goes to COLD then the check engine light comes on then the guage returns to normal...this would indicate a loose wire connection likely at the temperature sensor. The sensor itself could be bad too but I'm not sure it would correct itself if it was bad.
If you mean the guage goes to HOT then the wire could have worn insulation and shorting to ground somewhere between the sensor and computer OR a sensor going bad IF it can correct itself...again I don't know if this is possible.