First and foremost I'd recommend upping water intake and good fatty oils (Omega 3's in tablet, fish, or nut forms) because it's just that time of year when we kinda shrivel up lol. Fall & Winter transformations can be BRUTAL on my hair and skin.
It could possibly be build up (when I use heavy cones, if I don't rinse VERY well my scalp becomes very unhappy.) To solve that I clarify ever so often and adopted a low cone (if any) regimen. I like quantum clarifying shampoo because it's the only one my grass seems to like. Everything else RAVAGES it.
For those that don't want it to be uber drying, feel free to use it after a good heavy hot oil treatment.
Putting oil on top of build-up (if that's what it is) will only make it worse. Cleansing your scalp well then adding oil or pomade can help. I don't use anything heavy on my scalp anymore. Coconut oil, QB Amla Pomade, or a blend of oils work for me (for now). A majority of the time, I don't have to oil my scalp because of the products I use. I do use rosewater and glycerin on my skin, hair, and scalp. It really helps when I use it underneath oils or lotions. HTH