Your tamagotchi v5 may do that if the batterys are low. That used to happen all the time for me and my v5 and v5c. Just use a new battery and it'll fix itself.
Even if you just got it, the batteries could have been old ones.
I suggest replacing the batteries; but I'm not an expert, so feel free to ignor me. The same thing happened to my brother, too. Only, he had it for two weeks.