macbook air which has no software on it is always slow

been using Macs for 15 years. My 2013 MacBook Air is too slow, sometimes crashes and has to reboot. I dont do video editing, i use it for internet browsing and gmail only. Fed up with this, might have to buy a PC for the first time.

done so many restarts, backups, clean installs and i have the fastest fibre optic in the UK - its not the broadband. Its the macbook. Any ideas?