Scan 3XS

My excellent Scan 3XS custom 1150 has been rock solid for nearly 4 years now (hence first post) and all I have upgraded was GPU and SSDs but now it is starting to have issues and I can't afford a new one for another year or so (til after I pay for the very costly divorce!).

It doesn't boot at first and asks for F1 and goes into the BIOS at startup, if I just exit, it usually starts up ok but I'm wondering if this is an issue with the factory overclock? It's been so good for so long I know it can't last forever, but is there anything that can be done before it gets worse? The fans spin up to full blast on startup now too but I have loads of fans and CPU and GPU temps look fine so far. I have never messed with the overclock settings or changed anything in the BIOS. System is:

i7 6700K @ 4.6GHz (now seems to be running at 4 GHz?)
Vega 64
Z170 Ranger
32 GB Vengeance @ 3000
Corsair RM750i gold
Win 10

Can still get it working but something seems to be wrong somewhere and feels like it's about to fall over. I need the PC for everything, work, gaming, entertainment and need to get another year out of it hopefully. What are the options?

Thanks.