You probably have this issue because you've installed too many high resolution mods. Try removing some these, mainly detailed cars, re-textures etc. If you haven't backed up the original files then just google them. If that doesn't work, then download a fresh GTA3.img file (around 600mb) and then avoid installing too many mods in the future.
Jason took the words right out of my mouth(or the text right out of my fingers? lol)
I know this message is long, but it might just give you the help you need. You never know. If you have downloaded any high-res replacement car texture mods, trust me - I had this SAME issue - does the glitching happen in smaller close-knit towns where there are lots of houses, trees, and bushes close together? Like maybe...Palamino Creek? That was the worst place for me. Trees, houses, shrubs, everything - all reloading over and over, even when I was standing still for several minutes. Anyway, I would *guess* that downloaded car mods are causing it. If you have no downloaded mods installed in SA/SA:MP, then skip down to the last paragraph. My guess is that you do, and you should continue reading. :-)
Everyone has that "magic combination" of mods they can install before their SA:MP starts saying "Ok, enough." It's different for every system, depending on your specs. And just because you have a quad core blah blah with a Geforce blah blah and tons of blah blah RAM - that doesnt mean $hit. SA just doesn't like being modded. At all. I download a few high-res police cars, an ambulance from GTA4, a kick-ass Jaguar XK for my Jester, and a Honda Civic Si for my Flash. Man, they all looked awesome, and my game was running great. So I got on gtainside.com(of course) and found another one - a sweet-ass Honda Prelude Si. Well, SA:MP wouldn't have it. Textures starting going haywire in tighter areas - disappearing, reloading...constantly. I couldn't figure out why this was happening so suddenly! Then it hit me - "I just installed that Honda Prelude....hmmm...I wonder...." so I uninstalled the Prelude mod, and BOOM - like magic - everything was fixed. I was so pissed, cuz that Honda 'lude was flawless. *pout*
I don't know why, but like I said, everyone's computer has their own "magic combination" of mods they can install before their game starts acting up. My advice - start by removing the modern/highly-detailed cars - those are the worse, since they have lots of curves which translate to polygons(those tiny little triangle shapes that are put together like puzzle pieces to make 3D shapes)., Try to remember the last mod you installed before things started pissing you off. Okay, here's the question a lot of people have: "How do I uninstall just ONE car mod without restoring gta3.img or reinstalling the entire game?" Well, If you did not use SAMI (San Andreas Mod Installer 1.1) to install the cars, then you are in trouble... unless you backed up your gta3.img file, and even then, that restores EVERYTHING back to default. Here's one method: If you can find a clean copy of gta3.img somewhere, you can use an app like IMGTool 2.0 to manually open that clean gta3.img, extract the specific .dff and .txd for the cars you want to restore, then use IMGTool to open your *modded* gta3.img and *import* the clean dff and txd files into it, save, and rebuild the archive.
If you are not worried about hard drive space(like, if you have 100GB you can play around with), my best advice: backup a new different copy of gta3.img every time you install a mod, and name it gta3_modname.img, placing it somewhere so that you know where to find it, preferably in a folder outside of your SA game folder so it wont get fragmented and slow down your game. This is the EASIEST way to do backups when installing mods if you have that extra space to work with, since you can go back to any point and time. Think of it as your own version of System Restore for SA. :-) Anyway, uninstall your last mod first, then come back and try playing some SA:MP, and if that doesn't work, uninstall the next most recent mod, and try again.
I'll bet that one of your most recent car mods is the reason for the constant object/texture reloading. If not, then try the stream memory fix. There are several versions of it out there - and not all of them work for every computer....I had to try 3 or 4 before I found one that didn't totally f*** up my game. I Googled this: "san andreas stream memory fix download" and I found all of them. Like I said - you might have to try 2 or 3 of the different versions, especially if you have an older OS like WinXP, like me. I know it sounds like a lot of technical bs, but it's not. It's easy. Sorry for the long message, but I wanted to make sure you had as much information as I could give you. If more people would give detailed info, players could fix their problems a lot faster and easier. I hope this helps. If not, maybe it helped someone else who was reading it...
Your Friendly Neighborhood Medic,
Marius_Laru, AKA Marius Antonius, AKA Mr. Know-It-All, AKA Muddy Sr., AKA Pulse's baby-daddy