Question Laptop is completely stuck on Lenovo logo ?

[tcmgl]

Hi techs, I am wondering if anybody can help me with this laptop.

Laptop model: Lenovo ThinkPad P50s 20FL​

User was writing a document and then left to do something else. Later he came back and seemed like the laptop has gone to sleep, but when pressing the start button, it got to the Lenonvo logo and stayed there for a long time.
I suggested to hard shutdown and try again, and that did not help, even after trying several times.
So I took the undercover off, removed all the batteries, drained the power, removed the CMOS battery to reset BIOS. Left it like that for about 10 mins, then connected all the batteries and tried again. Still stuck at Lenovo logo.
In case it was the screen, I removed the connector for the built-in laptop screen and connected it to an external screen. Same thing

When you start the laptop and press F2 or F12 right away it does not do anything, just comes right up to the Lenovo logo screen and stays stuck.

If somebody can give me more suggestions or tell me what is the issue, would really appreciate it. I do understand the basics or PC and laptop repair, but this is a new one for me.

Thanks tcmgl

 

[NedSmelly]

This is a stab in the dark... perhaps a memory module failure? Maybe the BIOS is stuck in a memcheck loop. Might be worth trying a SODIMM swap.