What are your goals? You're a pretty decent size right now for someone who just wants to be in good shape and look good. I'll bet you look and feel better than 95% of guys your age. That said, if your desired goals involve gaining more lean muscle mass for whatever reason then, no, you're not too old to start running a cycle. As others have mentioned, it's best to get comprehensive blood work done first so you can establish a baseline for different important values like thyroid, LH, FSH, test (both free and total), estrogen, prolactin, and all of your lipid profiles.
Then, if everything looks good, do a search for "first cycle" and you'll get more feedback than you could possibly imagine.