Hello, I have done this on 2 occasions so far travelling with my partner on bikes then leaving them to walk a camino. Once into Paris and once into Prague.
In Paris, we booked the Nomad Paris Roissy hotel when we landed from Australia with our bikes (they had a shuttle that would fit the bikes, but think it may be suspended during COVID) and they stored our empty boxes for us for 6 weeks as we were returning to pack them up on our way home. Their luggage storage room was large and it would have made no difference if the bike was in the box. There is also a bike shop in Paris that were extremely helpful and you might give them a call. We had them repack our bike for our return and they stored them for us while we went off and did something else (don't remember how long that was for though).
Sébastien Reboux
Les Vélos Parisiens
0033 1 45 44 72 97
lesvelosparisiens@free.fr
In Prague, the SKY Hotel near the airport were also happy to store the bike (in the box this time) while I walked Spain for 6 weeks.
Needless to say we stayed at the hotel each time we left or picked up the
dirt bike.
I am sure there would be other hotels that would be happy to store your bike if you are staying at their hotel in and out.
Hope you find this useful.
sueT