It could be stress. I have had issues across the last 18 months.
Never had it before and always been a bit doubtful when people spoke about it. Is strange as now I can look back and see myself going downhill but couldn’t at the time. Girlfriend forced me to go drs to get sorted. Took a long time.
My issue was work and getting away from the situation helped. You need to try and work out what’s bothering you to deal with the root cause.
The advice above is good, especially alcohol and caffeine. Walks are good both as exercise and getting out for change of scene and fresh air. Be careful about walks before bed as the exercise can raise your heart rate and endorphins that make it hard to switch off