Dell precision T7400 does not boot properly

About 2 years ago, I started to detect some strange behavior with my Dell Precision T7400. When it booted, something like this message came up: "System alert! Thermal solution compromised. Please remove system cover and reboot". And then the fans freaked out sounding like a plain taking off. After a while (like a month) it usually calmed down, and these fan take-offs stopped. But they have always appeared again. These incidents have typically approached if I have for example ejected the soundcard to vacuum clean it or whatever, or inserted a new modem/unit before booting. I have tried many times to solve this mystery, by updating bios and drivers. I have googled it for decades, but I have always ended up calming the fans manually and storing the problem away for next "season". I have lately, heard strange and disturbing sounds from the computer, especially when booting. Now, it's different. The fans freak out as usually, but there is also these buzzing sounds appearing when booting, totally out of step. The screen does not boot, and the numbers "1" and "3" appear on the panel right with the USB ports on the front. If someone can help me with this recurring problem, I would be more than grateful. Thank you so much for your time!