Hi,
It may be that the battery is starting to fail. Even rechargeable batteries have a life span.
Here is a link to the ifixit [guide|38491] guide. It shows how the battery can be accessed so that it can be replaced. You will need soldering expertise and tools to complete the removal / replacement procedure.
Here is a link to just one [https://www.ebay.com/itm/Replacement-Tablet-Battery-for-RCA-RCT6077W2-3000mAh-7in1-Toolset-/291640721947?siteId=0&pguid=933fe7d115a0a88af7d17e89fff53fac&AdChoicePreference=true&rmvSB=true|supplier] of a replacement battery for your tablet. It is not a recommendation to use them. It is merely to show the cost of the part. There are other suppliers online that may suit you better. Just search for ''RCA RCT6077W2 battery''
If you find doing the repair yourself too daunting I suggest that you contact a reputable, professional mobile phone or laptop repair service and ask for a quote to replace the battery in the tablet.
Hopefully this is of some help