reasons for slow resolving - VPS

Hi - I've got a VPS account & when I connect to sites on the VPS, more often than not the browser times out. I click again & the site comes through.
I use Firefox & have tried in other browsers with similar results.
The VPS has 384mb dedicated RAM, with 512mb burstable - not much I know but...

I was wondering about possible reasons - could it be simply not enough RAM, could it be a bottleneck with the hosting company, could it be a problem in the setting up of the nameservers? What would seem more likely?

It's a shame as the tech support have been superb but it's too risky to use for reselling.

Have you ruled out the problem being you or your ISP? Try an Alertra spot check at http://www.alertra.com and see the response time of the sites from around the world.

Thanks Dan.
Alerta is for when your site goes down I think.
The sites on the VPS are 'up' but they just take a while to connect.
I've tried several websites that check response times & they seem to be fine but still I get this lag when I try to connect the first time with a clean cache. I've tried on different isps as well.
I'm trying hard to stay with this hosting company as in every other way I'm really pleased with them but...
I've got a feeling it's the bottleneck at the hosting.

Yes, alertra is a monitoring service, but on their homepage they have a free "spot check" tool. It tells you the site's response time from 7 or 8 locations around the world.

Thanks again Dan. I found it & all seems fine from everywhere - a second & a half slower from Shanghai.
So why might I be getting this lag at times? Very strange.