One way to find out if it is an issue that the CPU is not secured tightly and making good contact. Put downward pressure on the CPU while turning on the computer and see if it starts to boot. If it does then you need to repair the motherboard CPU latches or install a CPU Cooler that has it own latches that you install in the motherboard.
Possibly that you may have bent some pins while trying to install the CPU since you had a difficult time installing it. Check for any pins that may have broken off or are bent. Several other Users had damaged the pins on a Ryzen when the CPU came off with the CPU Cooler at the same time.
Basically, a loose CPU is not good. Remember that the motherboard probably vibrates a little from all the mechanical devices connected to it like fans and Hard drives. It may be enough to cause intermittent contacts with some of the CPU Pins unless tightly secured to the motherboard socket.