My back wheel will no longer spin freely im new to this site and don't know anything about how to repair bikes.
My Problem is
I put my bike into my shed (the shed is cold and damp) and never used it for 3 weeks, it was ok when I put it in but when I took it out to use it the back wheel has become very stiff, you're not able to spin it freely its just stiff. Im not sure where to start, is it the brakes or can it be something else ???

Any help would be great, the bike is less than a year old so not sure why this has happened.
Thanks

This is my bike
I am pretty sure the issue comes from your disc brake.
Check the brake pads first : there must be something wrong here because you say it was worse after you removed and put the wheel back.

I guess your brakes are hydraulic : sometimes when you store your bike in a humid place for a long time, the braking fluid will kind of "dilate", resulting in less space between the two pads, hence rubbing on the disk even if you don't press the lever.

Another test you could do is removing the caliper : if the wheel spins freely, that confirms my theory.

In that case, you need to push the pistons back to their initial position (using something to pry them apart, without damaging the pads). If you cannot, you might need to remove some fluid from the hose (there should be a small screw at the lever), but be careful not let some air go in the hose.