I'm 40 years old and I missed 2 periods, last month on the 1st day slight bleeding was there and was nothing for rest of the days..!
I'm confused please suggest what is it ?

It could be nothing, just a variation in your cycles. But at age 40, it's very common to start bleeding less and skipping periods, as you get closer to menopause. Menopause doesn't happen in a single day. My periods started getting lighter and less frequent around 40 and stopped completely at 50. But menopause can be 'final' much younger than 50, and there's no way to predict without expensive testing, so be prepared for a possible faster ending of your periods.

(There are other more rare reasons, but if you feel no discomfort, I would assume perimenopause.)