My phone dies around 40%-30%

The past two nights my phone has gotten down to between 40% and 30% and then just died (like it would if the battery had died but there was still juice left in mine) then when i go to plug it in its either not charging fast enough or there's something wrong with my battery because it turns on like it would normally gets to the lock screen for maybe 2-3 seconds and then dies again and constantly does that all night long. There's not enough time once the lock screen comes up for me to do a hard restart or even turn it off. My phone dies before i get the chance to do that. I don't know if I need a new battery or if there is something I can do to help this on my own