That is a strange glitch. I wonder if it's a problem with the Tama-Go or the figure? Hmm, maybe try taking the batteries out and putting them back in again? They might be in a little loose or crooked. Or when the glitch happens, push the reset button?
If this doesn't work, and the problem is very irksome and causes problems with gameplay, carefully take the Tama-Go apart and look inside it to see if there's a problem with it. Warning: only do this if you know what you're doing and are aware of the possible consequences of taking it apart. Be very, very careful, especially with the sound wires and stuff. (I've never taken a Tama-Go apart, but I have taken some Tamagotchi Connections apart and I broke the sound wires on one of them.)
The possible causes:
faulty figure
faulty Tama-Go
faulty batteries
incorrectly inserted batteries
the Tama-Go may have been dropped and loosened something inside.