Well the Battery is showing its age ;-{
You have two things coming at you age and cycles!
The age of your battery is now over seven years old (2015 - 2022) for a battery which lifespan is about five years. The batteries chemistry breaks down.
The cycle count is 138 currently, this battery has an expected cycle of 1,000 cycles (+/- 10 %) [link|https://support.apple.com/en-us/HT201585|Determine battery cycle count for Mac notebooks|new_window=true]
So I would say its already on borrowed time! Time for a fresh battery. You should be able to get at least 5 more years if you give it the needed TLC.. You might try resetting the SMC [https://support.apple.com/en-us/HT201295|How to reset the SMC of your Mac] but that will only buy you so much. Sorry ;-{
Here's the needed part [product|IF117-048-5] and here's the guide [guide|89284]