Your comment about head/neck being jarred is worth investigating. Many concussions create instability at C-1 to occiput and C-2 to C-1. The inflammation in this area can trigger a myriad of symptoms.

When riding in the car and you see a bumpy area, roll your shoulder and head forward. This will increase the shock absorbing capacity of your spine.

It took me years of discipline to get my head to neck connection stabilized. Sleep posture was the most important.