Credit rating: easy to destroy, hard to build up.
Making applications for credit does lower your credit score, and making several in a short period (i.e. less than a year) will definitely hurt it. I would recommend getting a credit card and using it for your regular monthly expenses (e.g. grocery shopping, paying bills etc) and making sure you don't go over your limit and you pay the minimum payment on time every month (or the entire balance). This will be a good start to establishing a credit rating.
Then just save up over the next year or so in your new job, while keeping up responsible credit use, and buy the car outright. In general getting credit to make a single "purchase" or what have you is a bad idea - unless that "credit" is a mortgage and the purchase is a house. It's realistically irresponsible, especially as you already have two motorbikes and a car based on your original post.