Website not loading from SERP clicks sometimes

One of my websites doesnt' load sometimes. Like, I'll have a buddy try to access my site, and they will say it won't load from a Google click theyll get a Google Chrome error "site can't be reached. took too long to respond"

Happens like 1 out of every 10 times i'd say and I die inside every time i hear about it or witness it myself.

I installed "uptime robot" which showed 100% uptime. Is that the right metric or no?

In general the site is just shotty to load. like sometimes it will load in a millisecond, sometimes it will take 10 seconds, sometimes it won't load at all.

Additionally, I have been getting a message from Google Ads (every once in a while, for different campaigns/links):

Destination not working

If the URL you entered isn't working, check to make sure it's correct, then resubmit your ad for review. If resubmission doesn't work, contact your web developer

What could be causing this?

I have zero tolerance for my site not loading if it's hosting's fault - could it be theirs? Why would uptime robot show 100% uptime?

My host is cheap and crappy and every time i call them to explain the issue, they say "dur, works for me. try a private browser"