Dell Latitude Suddenly Running Extremely Slowly—Could the Charger Be the Cause?

My Dell Latitude 5590 has 16GB of DDR4 RAM, an 8th-generation Intel Core i7, a 1TB M.2 NVMe SSD, and Windows 11. It worked well for everyday use and light to moderate gaming, but about a week ago it suddenly became extremely sluggish. File Explorer can take 30 seconds to open, and some applications take several minutes. I checked for malware, looked for unusually high resource usage, updated drivers, removed temporary and unnecessary files, replaced the thermal paste, cleaned the fans and vents, and even performed a factory reset, but the problem remains. One unusual detail is that the AC adapter has started buzzing whenever I turn the laptop on. Could a faulty or underpowered charger be forcing the processor to run slowly, and what should I test or replace?