u/BoxUsual2230

If it matters, i have a trek marlin 6 with shimano altus gears.

The bike wont stop changing gears whenever i pedal, im not touching the shifter at all but the chain goes both up and down in gears.

I usually keep it outside, so im not sure if the weather is affecting it.

I went on tiktok and youtube for tips and both had no info that seemed useful, so here is my last option. Please tell me how i can fix it and what equipment i need to use, thanks.

UPDATE: thanks to the answers, the issue has been fixed.