MacBook Pro battery/charging issue

Hi,

Something strange is happening with my MacBook Pro lately. If it's been a sleep for a while and I then open the lid, it turns on for a good 10 seconds and then dies as if the battery is dead and won't turn back on unless I plug in the charger.

Once the charger is plugged in, I can turn it back on and it will say I have plenty of battery left. I am also able to unplug it and it will continue to work without being plugged in.

It's about 4 years old now, but except for the issue with dying after waking up, it will still go for a good 6 hours on a single charge. Battery health in system report says "Normal".

Any ideas what could be happening here?

Thanks!