The earliest example I can think of is Heraclitus, a 6th century BC Greek philosopher, of whom Diogenes Laertius said "He states, however, that there are vessels in it, turned with their hollow part towards us; in which all the bright evaporations are collected, and form flames, which are the stars; and that the brightest of these flames, and the hottest, is the light of the sun; for that all the other stars are farther off from the earth; and that on this account, they give less light and warmth". Similarly, of Archelaus, from the 5th Century, "He said that the sun is the largest of the stars".

So it was, at least, believed by some thinkers of the time that the sun and stars shared a similar nature, in that they were fiery masses that orbited the Earth or the centre of the universe (with a distinction being drawn in that the Sun is larger/brighter/more distant than the other stars, or that the other stars appear to be fixed with respect to each other, whereas the Sun and planets are not). That is slightly different, however, from saying that the stars are suns, which in modern parlance would imply that the stars are orbited by other worlds, like the Earth around our Sun, which these thinkers definitely did not suggest. Also, to say that the stars are like the sun isn't very helpful without first explaining what the Sun itself is like (which is by no means obvious) - in Plato's Timaeus, in fact, it is argued that the Sun was, in part, created by a God in order to provide guidance (in the form of timekeeping and mathematical knowledge), so someone from the time could very well argue both that the stars were made by the gods to guide men and that the stars were suns.

So I don't think it would necessarily be accurate to say it was a common view at the time, but it also wasn't one that was unheard of either. The phrasing, however, is decidedly modern, so it could be considered implausible on that count, at the very least.