4 year old computer check that the air vents are clear of dust and fluff.
If so inside will also need cleaning out.
Maybe some of your drivers needing updated.
What security programs have you got and are you connected Via Wireless.
Surface Pro (2017) vs Surface Pro 4
20 groundbreaking 3D animation technologies coming to Siggraph 2017
iPad Pro 12.9 vs Surface Pro 5
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.