What is #1 cause of pain underneath left shoulder blade?

Might be onset of frozen shoulder syndrome. Often only cortizone shot may help. But this is guess work plus having had the syndrome on my part. For all I know, your pain could come from a vaccine shot. Even gall bladder problems or heart disease can cause chronic shoulder pain. A doctor might sort this out, given time.

Remember, I'm not a medical professional. Any suggestions here actually can potentially make things worse, given I have no way of knowing the underlying condition. Any suggestion I have might work but might waste your time when it would be better being used to sort things out with a medical professional. Just because the shot or pain reliever proved ineffective is not a reason to suppose the next form of treatment on the doctor's check list also will not work. But serious chronic pain is nothing to ignore as it will wear you down in short order.

Till then, there are specific stretches which might help if it is related to muscle injury or frozen shoulder. The sort of pain you are talking about tends to finally make it very difficult to sleep.

Upper Arm Pain Exercises Medi Dyne

You might also google for exercises on the Mayo Clinic site. That site has a symptom checker too and might help you rule out some things.

the dosage limit is in the how to take directions on the packet

not spider veins ?

does dr google have images or a medical site give
symtoms or name for it

shingles ( pictured )spreads a short way either length of the affected area

anything is "probable cause " in the eyes of law enforcement , shame but there it is

Finding good seating is tough.
Better models will have more adjustments on the seats but if you search you may be able to find a mint low mileage 1996 Honda which is like new and then you will have a seat you know works for you.
Otherwise.....you could take your seat with you.
Put it into the newer vehicle.

Pain on left side causes of the spasms are unknown, but can be triggered by mental stress, improperly carrying a heavy object, or stretching too much. People with sedentary lifestyles are more prone to back spasms.The typical symptoms of this kind of left side pain are inability to bend in certain directions, and sharp shooting pains. http://www.elswickchiropractic.com/

If it is not on the left side of the motor underneath, near where the transmission bolts to the block then it is a model with the remote filter.
Remote mount should be also on the left side closer to the radiator support accessed from under the hood. They are kind of a pain in the B-U-T-T!