Hi @trathfon62, I think it depends if it's a smooth ride or bumpy and jarring. Some people with osteoporosis have gotten spinal fractures from sneezing. Can you check with your treating physician or a physical therapist?
With respect to vibrations, some people use a high intensity vibration platform exerciser to improve bone density, although Margaret Martin, a physical therapist who specializes in osteoporosis has warned about the dangers of this. Both she and Sara Meeks endorse the low instensity vibration exercisers which were developed in conjunction with NASA.