So i randomly get this weird rash on the top of my hand out of nowhere. its bumpy and red but the bumps arent that far apart and it only itches for a couple minutes but then the rash goes away in like an hour?

Is it just one hand or both hands? If not both hands, is it always the same hand? A rash that comes and goes that quickly is usually due to an exposure of some type. So, keep track of what you are doing right before it appears to see if you can figure out what the exposure is and then try to avoid it. If it becomes more frequent, lasts longer or becomes more bothersome, then see a dermatologist!