I would recommend to go for Mechanical Engineering. Automobile and Mechatronics come under the umbrella of it. As far as scope is concerned, Automobile Engineers are hugely employed either in Automobile companies Or in manufacturing sector. As both of the sectors are not doing great, there are not enough companies in the market nowadays. Also the companies which are recruiting paying around 18 - 20 K in the starting.
Choose it if you really have a passion towards it. I meet many people who go for this branch because they love cars and technology. It's good to love Cars but its Engine
I can't say with 100% assurance that you will, but math is not exactly a prerequisite for software companies.
First of all, find out what you actually want to do in your life. You are already done with your Masters 4 years back and still not able to decide.
I would recommend you to take the test:
It will help you to decide clearly.
What kind of exams are you looking for?
There are more that 20 of them.