I'm looking for a hobby to try that's similar to needle felting. Do you have any suggestions?
Yes, here are some hobbies that are similar to needle felting:

Wet Felting: This is a process of matting, condensing, and shaping fibers using soap, water, and friction.

Sculptural Felting: This involves using wet felting techniques to create three-dimensional sculptures or objects.

Knitting: Knitting is a method of creating fabric by looping yarn through needles.

Crochet: Crochet is similar to knitting, but uses a single hook to interlock loops of yarn.

Embroidery: Embroidery is the art of decorating fabric with needle and thread.

Cross Stitching: Cross stitching is a form of counted thread embroidery that uses X-shaped stitches to create a design.

Weaving: Weaving is the process of interlacing threads to create a fabric or textile.

These hobbies are similar to needle felting in that they involve the manipulation of fibers to create decorative or functional objects. They each offer their own unique challenges and techniques to explore, and you may find one that you particularly enjoy.
Which one is the easiest to get into if you are already decent at needle felting?
Sculptural felting is closely related to needle felting. If you learned needle felting, sculptural felting is just making more elaborate and complex sculptures, reducing the need to learn new techniques, but still having a big creative potential.

Wet felting is still felting, meaning the end product will be similar to needle felting, but the process is quite a bit different from needle felting. However it can be combined with needle felting and structural felting techniques to create even more elaborate pieces.