Unforced and Unbidden

Unforced adjective - Done, made, or given with one's own free will.

Unbidden and unforced are semantically related in voluntary topic. In some cases you can use "Unbidden" instead an adjective "Unforced".

Unbidden adjective - Not searched or asked for.

Unforced and unbidden are semantically related in impulsive topic. You can use "Unforced" instead an adjective "Unbidden", if it concerns topics such as agreeable, willing, spontaneous, voluntary.