Depends on why you want to do it.
If you do it for knowledge, skill and because it interests you, go for it. It will help you to increase your selfconfidence and you will have knowledge to share, show and apply.
If you do it to solely to impress the employer at the company you are applying for, then you shouldn't. As Kilroy put it, a certification that is also accredited is probably better, but there are disadvantages: it costs a lot of money and it often has a time limit after which you would have to get the certification again. Employers often pay for certifications, so I personally wouldn't do any before the apprenticeship.
My advice: Look for things you like, learn things you like and do projects you can show. The employer wants to see that you are interested and motivated. This counts more than your actual skill and knowledge, because you are applying to learn from them and they usually like to get unspoiled people, who didn't had the chance to learn things the wrong way.