Have you looked in Processes to see if anything is hogging the CPU?
Ctrl/Alt/Del then look under Processes tab, the only item which should be showing 97% or thereabouts is System Idle Process, all the rest should be at no more than 0% to 4% approx.
OnePlus 5T review: Hands-on
Illustrator Andrés Lozano on his improv line work, brazen use of colours & hand sketching
iPhone X review
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