I don't have this, but I wonder if it's some kind of Restless Leg Syndrome?
Maybe.

If it's all on one side, maybe you injured it, or pulled a muscle at some point? I get aches and pains from injuries I had playing sports 20 years ago.

If it persists, or you are worried about it, I do think you should see a doctor.

Hope you feel better soon.

I don't mean to scare you because it could be nothing but a piched nerve from sleeping on that side too long but my ex had a pain similar to that and they put her on iv's in the hospital for 3 days to try to dissolve a blood clot in her leg. Luckily it worked and she is a live and well.

If I were you, I would definitely see a doctor if it persists!

Yes, I agree with Bob - it sounds like you may have a compression at L5-S1 spine level.
Most of the time this can be relieved with medication and physical therapy -
Pressure on the nerve is not good long term.
However, there are serious issues that can cause nerve compression - like a mass on the spine or severe disc protrusion, especially if there was a fall or a traumatic accident in the past.
It is best to go see someone, they may or may not order an X-ray, depending on your age and risk factors.
If you stick a pillow under your pelvis and that relieves the pain, then something is pinching the nerve at the spine

Do you guys think it can be due to sitting down for long hours at work?..

Blood clot?…hmm.. I’m contemplating going down a long traitorous google hole but maybe I shouldn’t?..

It is concerning that this is on one side. That makes me think it could be the serious things that others have mentioned. Don't wait to seek medical assessment.

If this turns out to be nothing serious but more like muscle, joint, bone irritation, consider trying Theraworxx magnesium skin cream. I often get pains in my thighs, legs, feet, ankles. But mine is usually both legs in same pain. My blood work and X-rays came out okay so I finally found this over the counter stuff, or on Amazon, and it is a game changer. I need to use it morning and evening and for 2-3 days when in a pain flair. It dries fast. Other people try magnesium supplements but they don't do it for me, don't help.

As others said, this surely can be something spinal, blood clot, or even just wearing old, unsupportive shoes. It can be from sitting too long and compressing your muscles and joints in the hip and pelvis area. If this is nothing serious that medical doctors can find, some people find relief from chiropractic or massage work.

I had another thought. Research "tight IT band" as this is the structure that goes down the outside of the leg from hip to below the knee. It gets tight and can hurt all up and down, referred pain into the hip. Might not be what you have but I thought I'd mention it because it is apparently very common.