New build not starting

Dec 15, 2018
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Hello there

So, I assembled a semi new computer. When I start it, the CPU and sys fan spin, I get a beep before it enters a restart loop.
Without RAM it starts fine, no restart loop.

Does that mean the RAM is faulty or could it still be a faulty mobo?
 
The next best thing I can put my hands on is the INTEL Core i3-8100 for $140 compared to $60 for the Celeron which should be good enough for my mom's needs.
If I knew this old CPU isn't compatible anymore I'd have bought AMD. INTEL is so scarce these days.