Voltage/Electrical Problems

Sounds like your battery is about to die or the alternator. Take it to an auto parts store to see if they are working properly

Does the car start normally? Is there any problem at idle? Any warning lights on?

If you want to run a simple test on the electrical system, check the voltage across the battery terminals. It should be about 12.5V with the engine off and 13.5V with the engine running.
A voltage below about 12V with the engine off would indicate a battery that is either discharged or defective, and if the voltage is the same with the engine running, your alternator is bad.

If the only problems are during a shift, I'd suspect a loose connection somewhere- probably something behind the gauge cluster, since all your problems are in that area.