Usually thats the case, sometimes it will be fixed if you replace only 1 RSX nec tokin (4 caps).
If your console turns off instantly its RSX but if it turns off after 8-10 seconds then its most probably CPU and you can fix it with piggyback method by adding 2 or 4 caps near CPU nec tokins.
Your NEC tokins are going out.
You can fix it easly without replacing nec tokins, since those are somewhat still working you can just add 2 tantalum capacitors (330ohm or 470ohm) near RSX tokins (piggyback method).
I've done this on multiple consoles and it works great.
I worked on alot of 3DS XL consoles and never had this issue.
Issue is when I turn off console and leave it for 10-15 minutes it wont turn back on until I remove battery and put it back in again.
If I turn it off and wait 3-5 minutes it will turn on normally but if I wait longer (10-15 minutes)...
I may try the new ram site, and download more RAM to my Switch. Not sure if ddr3 is the right ram
for it tho. Edit- no it uses floppy Ram, just like @AncientBoi