I had some burning muscle pain & muscle spasms with my RSI/TOS/myofascial pain.
The spasms are locked up muscles that contract- pulling down & around your cervical vertebra , thus the grinding /crackling..
myofascial - Google Search

It took a long time with a very good chiro & expert PT and my own at home therapy to resolve it..and off work..

look up trigger point chart info - there are charts to locate your pain and see where trigger points might be. then info on how to manually press on them to release them.. Some you may not be able to reach by your self, the ones on the side of the neck might be near a main artery so a professional might be best for those if you have them in that area..