not sure what kind of gas you're running, but I noticed all of our rangers when the cold started in november (below zero temps) would start up cold, and if you touched the accelerator pedal before 20-30 seconds had passed, the engine would just die. We found out that this problem went away when we got our load of wintertime unleaded in 91 octane (no ethanol). There is a difference between summer and winter gas. and it'll make a big difference in how your engine acts until it's warmed up.
if you're running ethanol in your gas, then that could be the problem all by itself. polaris rangers don't run good on any blend of ethanol. it's complete junk fuel, and these things know it.