Hi i wonder if I could ask for some advice?
I’m rather new to the MTB scene and I’m just starting to encounter my first technical problem, I though I’d seek some help here and try to fix it myself before taking it back to the place of purchase.
Said problem:
The rear gears seem to be changing themselves/ slipping /changing when I apply pressure to the pedals and I’m not sure what is causing this? is this a common fault that is easily resolved?
All advice welcome,

thanks … Paul

If the bike is new then most likely the gear cables are stretching at settling in, so the rear one has ended up a little bit slack.

Where the cable goes onto the rear mech its got a barrel adjuster… tey turning this a couple of clicks anti-clockwise (this’ll effectively tighten the cable). See if that improves it, remember how many clicks you do so you can always set it back, but it might take a couple more. If still no luck revert it back and just take it to someone in the know, it’ll only be this kind of adjustment thats needed.

guide here

Very detailed instructions (should have been done by shop though) what poster above says will probably do it or the one on your gear changer as you can play with that whilst pedalling
Back to shop to sort for free?
Dirt and grit in cable can also cause this but SRAM are usually less susceptible to this than Shimano (though this is not a universal view)

all of the above is good plus if your bike is full suss, also check that your shifter cable isn’t being pulled tight as the bike squats when you accelerate can cause ghost shifting

If you have an X.0 rear mech there is no barrel adjuster on the mech, you need to follow the same advice but with the adjuster on the shifter.

People,
Many thanks for the help I shall give the adjust on the shifter a tweak and see how I go.