What are the reasons for waking up daily at 3 AM with dizziness, lethargy, fever, and sweating, difficulty returning to sleep until 5 AM, and inability to sleep for the rest of the day?

What you are suffering from may be a psychological or physical illness, or a whisper (waswas). In all cases, you must resort to Allah through supplication, persist in acts of obedience, refrain from sins, and maintain your remembrance (dhikr). There is no objection to presenting your condition to a specialist in psychiatry or physical medicine. Do not worry, for Allah has made a cure for every disease. Supplication has a great effect on the heart, and it is worship.