How can I get a postdoctoral position in neuroscience after completing my PhD in Mechanical Engineering?
I have the same issue, I recently completed my Ph.D. in computer science. Accordingly, I have applied several times for post-doc positions around the world and I was able to get only three interviews. Unfortunately, none of them was willing to give me the post-doc position. 

Based on my short experience, it will be better to submit your application for a Fellowship with peer review process such as Marie Skłodowska-Curie programme. Open up to the world (China!).

Best wishes.