Paris hotel?

Well, I alternate between Hôtel Muguet and Hotel Relais Bosquet in the 7th near Rue Cler. It's not "central" for most people but I can walk most places from there including Notre Dame.

Not sure what your budget is when you say "not too expensive". Hotel prices fluctuate and both of these hotels have different prices for many days of the week. It will also depend on when you are traveling as to what the price structure is.

Both have AC which you may need in June, especially if you are at the end of June.

Lotsa folks will have lotsa recommendations.

We spent 3 nights Hotel des Grandes Ecoles in September. 5th Arrondissement, steps from where the Hemingways lived in Paris, very near Rue Mouffetard, near the Pantheon and the Sorbonne, walking distance to Musee Cluny, Jardin des Plantes, Luxembourg Gardens, the Left Bank and Notre Dame. The “walking distance” locations, which are the farthest from the hotel, are roughy 15 minutes; 12 to 18.

Our review is at
https://community.ricksteves.com/travel-forum/france-reviews/paris-hotel-des-grandes-ecoles

Hotel Lenox Montparnasse in the 13th.
Have stayed 3 times.
Rick’s tours use it.

hey hey manager
few posters have listed some hotels. not knowing what you mean by central, another person with "not too expensive". would help to know your budget in euros. how many is "we", any mobility issues (stairs/steps with luggage, need a lift/elevator), how many beds,
A/C. remember check in time is 3-4pm and check out time is 10-11am, unless you get approval for early/late check in/check out
paris is always busy and crowded, especially with june being high season with many travelers. check booking.com and left side has filters for you to look at, see what you like and book it and forget it. many people doing the same thing you are doing/hoping for.
book early since you may get slim pickens or high prices. it's not only europe it's all over the world. enjoy & have fun, enjoy
aloha

Hotel Muget.

Hotel Le Regent. I stayed here for a week in September. A good price for Paris, excellent location.

Booking.com is good for research. You can then book direct or book through Booking.

I stayed at Hotel Mistral in Montparnasse earlier this year and liked it.