Do I need to pick up my luggage when connecting in Paris?

Assuming this is one ticket NYC>MRS, and you check your luggage like that, then it would be checked through to Marseille and you would do customs there. As far as the Yotelair at CDG, the website states that you can only stay there if you have a boarding card for a flight departing from Terminal 2E. Does your flight to Marseille depart from 2E?
https://www.yotel.com/en/hotels/yotelair-paris-charles-de-gaulle
Edit: Checking the Air France website for a random date in July, flights to Marseille depart from 2F.

Immigration is at CDG, customs at MRS. There is nowhere at CDG to recheck luggage to a final Schengen destination.

How long is the CDG layover and are you on a single or separate PNRs to MRS?

I must question Frank's response. It doesn't matter that Paris and Marseille are in the same country with regards to customs. Assuming that the entire journey is on one booking, the bags will be checked through to Marseille and the walk-through customs process will occur also in Marseille. In Europe, the bags originating outside of the EU have special tags with a green stripe so the customs officers in Marseille can easily see what is arriving from outside the EU. All EU airports, not just EU entry points, have customs desks.

Thanks for the responses! My layover in Paris is 7 hours, so I'm planning to check into YOTEL to sleep for a few hours. My flight NYC -> MRS is all in one booking, and I believe Sam is right that the flight from CDG -> MRS is not in the same terminal as YOTEL, which is why I want to go to YOTEL before exiting the terminal after arriving at CDG.

My memory of CDG is a little dated, maybe 9 years, but every international arrival I have experienced, save from Canada or Ireland where I cleared US immigration before boarding the flight, you will be herded off the plane through a separate one-way corridor to immigration. Then you will be outside Terminal 2E and would have to reenter the airside departure area to get to the Yotelair. If you do not have a current 2E boarding pass, you will not be able to get to the Yotelair. You will not have the option of hanging out in the airside 2E area.

The Sheraton is still an option for quite a bit more money.

Are you sure that Yotel offers day rates? The information that I have is that checkin is available only after 6pm.

The Sheraton is closed but there are other nearby hotels that have day rates such as the Ibis at Roissypôle on the CDGVAL line.