Is my GPU throttling my PC performance?

I upgraded my PC in 2021 and updated every part except for my GPU, because it seemed fine even if it was a few years old, but now I wonder if I shot myself in the foot. About a year into using the PC, I started having issues with it.

After booting up, *everything* is slow. Start up takes forever even with SSD, programmes take ages to get going, and most games need to run for a while before they reach normal performance, and 'normal' isn't great. I rarely shut down my PC because it takes so long to get everything back to normal, and it spends most nights on sleep mode. Recently the performance has got even worse, and programmes like web browsers or Excel will freeze randomly.

The PC isn't overheating, there's no dust inside or blocking the ducts. I have run disc cleanups, and emptied my storage. I've run virus and malware checks.

* Processor: Intel(R) Core(TM) i9-10850K CPU @ 3.60GHz (20 CPUs), ~3.6GHz * Motherboard: ASUS® TUF Z490-PLUS GAMING (LGA1200, USB 3.2, CrossFireX) * Memory: 49152MB RAM * GPU: NVIDIA GeForce GTX 980 Ti * OS: Windows 10

Thanks!