first boot is always slower anyway as Donut needs to Dexopt all the apps and it doesnt until you run them so rerunning preused apps will be faster but yep i know its not particually quick, could you do me favour and open the app menu goto dev tools and find the option that says show cpu usage and turn it on, it will give a red and green bar at top of screen can you look at the green bar and see if it moves or seems stuck at a certain level all the time ?