I am nearly 30 weeks and have had this pain intermittently. I think it is baby sitting on a nerve or baby having growth spurt as I usually get mild cramps. I also seem to get it after doing lots of walking. At first, it used to freak me out as I thought my cervix was opening up.
As you are 36 weeks, I guess weight of baby is a factor. Maybe mention it to MW.
2 things spring to mind depending on where the stabbing pain is. First is spd if the pain seems to be on the bone at front of your 'fairy'. Lots of threads about this if you think it's this but lucky you only getting it at 36 weeks! I'm nearly 22 weeks with DS2 and it's starting for me again (was at 18 weeks with DS1)...
Second is pain in the cervix, inside and up if you get my meaning... That, especially at this stage is probably because your baby is starting to move downwards getting ready to engage and therefore starting to 'stretch' the area. Don't panic, this is normal, tho mention it to your midwife anyway when you see her. Hope this helps..