Is it common to start experiencing osteoporosis at 46?

No, but its possible: Osteoporosis, aka decreased bone mass, becomes more common as we age. However, it is dependent upon many factors such as the age of the onset of menopause and the quality of your bone health as a younger person. It would be out of the ordinary to have osteoporosis at that young of an age but not impossible. If you are concerned, you should discuss it with your doctor.

Decline of bones.: We start to lose bone in our mid-30s, at a rate of about 1% per year. Once women reach the menopause the rate accelerates to as much as 10% per year. So OP at your age could be from (1) early menopause (assuming your female), or (2) bones starting out weak from your youth, maybe from chronic low vitamin D levels or parathyroid condition.