Why does device die but when charging theres a solid green light?

im listening to music and all of a sudden it dies on me, so I go to charge it and there's a solid green light, meaning it is fully charged, but it keeps repeatedly dying on me. when I keep the charger in and turn it on it quickly flashes red but goes back to solid green. is there any way to fix this? am I doing something wrong? it connects right away and does what its supposed to do, but dies all of a sudden and it wont charge because its saying it fully charged, im just so confused about this.