Delay in acquiring satellites and inaccurate GPS

It takes 3-5 mins for GPS lock? Eek... something wrong there I think. Where are you located and is there anything that could be blocking GPS (tall buildings, trees, etc)?

What firmware are you running? 4.7?
Have you turned the watch off/on?
Have you synced with Garmin Connect over a computer recently to take advantage of the GPS caching?

If nothing is working, you could try a factory reset. Just make sure you've synced up with Garmin Connect so you don't lose anything.

Connected to my PC yesterday. Running version 4.7.

Area is typical urban, trees and 5 storey buildings, was no problem before, as I mentioned typically I'd get a lock in 20 seconds or less.

Put the 235 in my balcony after my run, got a lock in about 30 seconds, but what's been happening is the last 20 minutes of my runs the GPS plays up, split times are out, and the map on GC has me running through buildings.

As long as you're getting a GPS lock, it sounds like a tracking issue or you're losing your GPS lock momentarily. I get them every now and then. I hate when it happens.

What are your GPS settings? You could try playing with those options. I spent some time months ago figuring out which setting combinations worked best for me.
Activity Settings > GSP > Normal/GPS+GLONASS (mine is set to GPS+GLONASS)
Settings > System > Data Recording > Smart/One Second (mine is set to Smart)

Another option, you could install the latest beta firmware to see if it changes anything. http://www8.garmin.com/support/download_details.jsp?id=10450 I've been running this, and it seems stable.

Worst case scenario, try a factory reset.

Wish I could offer more help, but that's all I've got.

I experienced the same thing yesterday on beta FW 5.07. I couldn't get a GPS lock on any activity or using a GPS widget. I tried in several locations. Weather was clear, watch was synced, settings correct and tried restarting. I finally got a lock after several attempts and waiting about 10 minutes. First time this has happened. Everything is working fine now this morning.

Update: I for got to add earlier that I use the Android app GPS Test on my cell. While attempting a GPS lock on my watch, my cell phone app immediately was viewing 22 satellites, using 9, with a 23' accuracy. I chalk it up to another 235 disappointment.

Got Glonass on and is set to smart recording.

With other Garmins in the past I'd get a bad run like I've been having maybe once in 30 runs. I've had 4 in a row.

I'll do a few more runs and see if there's any improvement before doing a factory reset. If that doesn't work looks like I'll have to install the beta version.

I held the power on/off button for about 10 seconds today till the Garmin logo appeared before turning on, don't know if that was a soft reset or not. Didn't make any difference.

Gone from bad to worse I'm afraid. Won't find satellites at all now. Have done a soft reset, restored factory settings, and restarted it, no luck.

I've contacted Garmin support, let's see if they can solve it.

What does the GPS version say under Settings, System, About ?

Sounds like you have done a Hard Reset - which will delete the cached satellite position data. It will then take a lot longer to get a fix again. Should of course do so after a few minutes.

I haven't done a hard reset. There's another thread about how to do it, and I definitely haven't done that.

GPS is version 3.0

Hard reset is the one when you hold down the power button until it turns off - which sounds like what you did. This deletes all cached GPS position data.

A master reset is the one where you clear all settings.

GPS version being 3.0 is good - I was just worried that it was 0.00 which indicates a hardware fault.

I am not sure where you are now trying to get a GPS fix. Suggest just leaving in the most optimum place you can. One possible dumb question but you are in activity profile where GPS is actually on?

GPS is definitely on ;). Took it yesterday to the countryside, not a tall building in sight, left it till it auto powered off and all that time it never got past one flashing bar on the GPS scale.