Answer:
There are no fully documented portraits of Shakespeare painted when he was alive. The best-attested image of him is the Droushout engraving, which appears in the First Folio. Its accuracy as an image of Shakespeare is attested to by many people who knew him. This is the best-known image of Shakespeare. There is also the monument in the church at Stratford, which was paid for and approved by Shakespeare's wife and children as an accurate portrait. It is quite similar to the Droushout. They both show a man with male pattern baldness, a small beard and moustache (unusually small in an era where full pointed beards were the style) and a broad forehead.
The best-authenticated painting of Shakespeare is called the Chandos portrait. Even this is not considered to be properly attested, although it is a popular image.
Every few years someone claims that this painting or that is really a painting of Shakespeare made from life. The evidence for these claims is usually quite scanty, but it makes for a good news story.