I have a PAL SNES (UK). All my games are PAL.
For a while now my old SNES would reset occasionally but I thought it was just my system aging badly and it didn't really affect my gaming sessions. Another issue I had was games, some time ago I posted a thread about DKC2 not working correctly, and recently I bought another one for a good price and also purchased Kirby's Fun Pak and I got the same issue with DKC2 and Kirby wouldn't load at all, it later turned out to be my old SNES so I replaced that with a new one and the games work flawlessly now.
Games I haven't been able to get working however are Street Fighter II Turbo and a new game I bought (Yoshi's Island). Street Fighter would either freeze at the opening or freeze once I make it past the title screen and proceed to the character select, oddly enough I can use the options. Yoshi's Island likes to reset at the Nintendo Presents screen and the intro, what it would do is either reset when the nintendo logo appears or when I am at the intro and I press start, a white box flashes (sometimes) and it goes back to the nintendo screen.
I am starting to believe that the PSU that I am using is what is causing the resets for Yoshi at-least but I can't be sure. The person I bought the Yoshi from told me that it worked perfectly fine, and I used Surgical Spirit (rubbing alcohol) and a Q-tip to clean the contacts. The PSU I am using is not official, it is a really old IC universal regulator (I am not really familiar with this but that is what it says on the PSU >_>) which my parents got for me when I was still a kid. Is this why Yoshi resets?
I think Street Fighter is a lost cause, but I hope this is the case with Yoshi, this game cost a lot.