Josh- it could be tight hip flexors, or Iliopsoas. They are actually 2 muscles, the iliacus and psoas major. The psoas major is the larger of the 2 and originates on the anterior(front of) lumbar vertebrae and attach to the femur. Many people who do a lot of sitting have tight hip flexors resulting in low back pain.
An individual will try to bend forward at the waist and try reaching for the toes to try to stretch the low back, to no avail nor relief.
Try the 'Samson stretch'(CrossFit warm-up) and even try to elevate the back knee to get an even better stretch.
That's my 2 cents.