phone keeps displaying the nokia name going on and off on the screen.

Hi,

Try connecting the charger with the phone off. Does it charge at all?

If so, allow it to fully charge and then try using the phone, without the charger connected.

If it starts to fail again shortly afterwards, switch the phone off and reconnect the charger, then switch the phone on and see if it now works OK, with the charger connected.

If it doesn't try the advice offered by @lpfaff1

If it does the most likely problem is that the battery is failing and needs to be replaced. How old is the phone? Even rechargeable batteries have a life span.