Have been having muscle spasms on the back of my right thigh right underneath my buttcheek off and on for hours now. is there usually any concerns with muscle spasms?

Muscle spasms are quite common in otherwise healthy people. Sometimes these occur due to electrolyte imbalance but most often the cause is difficult to find. One medicine that works well is quinine taken as a prescription from your family doctor or you can try using Tonic water which also contains quinine. If taking this helps, you can use it as needed.

Not usually but can be concerning for dehydration or electrolyte imbalance. If persistent can check labs and treat at needed