I’m not sure if Jeff Beck currently wears a wig, but he has had hair loss over the years, as many people do naturally.
He also underwent hair transplant surgery. I couldn’t find any credible sources that confirm or deny that he wears a wig, so it is possible that he does, but it is also possible that he doesn’t.
It’s worth noting that whether or not he wears a wig is not really relevant to his music or guitar-playing abilities.
Many musicians choose to wear wigs or hairpieces for personal or professional reasons, and it is not uncommon in the entertainment industry.