iphone 6s only turns on when connected to charger

my iphone 6s only turns on when connected to charger it also has unexpected shutdowns . i am unable to use my phone since after its boot up it suddenly shuts down. i updated the phone and also tried rebooting and restoring it does not turns on. the day before this problem i have updated to ios 13.2.3 and since the next day this problem started. can somebody help me because i dont have another phone to use and am unable to buy another one in present condition.