PC restarts automatically!

So guys I've had the problem and things i did to counter it Ram clean Ram slots changed Dust clean Power buttons changed Power chord changed Reconnected PSU things

Even when the hard drives were removed the pc still restarted automatically after 2-3 seconds

Core i7 3770 16GB ram, msi mobo Rtx 3050, 500watt psu

So, i removed the graphics card and plugged it back again

After doing this, the pc runs fine

Don't know what the problem was or is? Can someone help me to understand