From your description, as the rash appears and disappears, this could be the result of an allergic reaction
In all cases of allergic reactions, we need to find out the allergen (the causative agent).
My advice would be to monitor the food you consume, try to think back and remember what you ate or came in contact with on the days you experienced the rash.
Allergens range from food products (fish, etc), clothes (cotton, silk, etc), seasonal (more often in autumn and spring), insect bites
, accessories (deodorants, perfumes, henna, etc.) , medication, and many more.
Think back and see if there were common items you consumed or came in contact with when the rash occurred. Try to change your bed sheets often, and install grills or meshes for your windows.
Protective lotions like calamine
lotion, could help in providing a barrier between you and the contact allergen (if external).
Finding the allergen and avoiding it can help you prevent the rash completely.
Also, I would advice you carry an anti-histamine
drug that best suits you at all times to avoid a sudden allergy
caused by accidental contact with the allergen.
Hope this information has helped you.
Wishing you the best.