It is very unlikely this would be hacking. IMHO it is more likely to be a software glitch or the touchscreen needs cleaning. Lower probability but still more likely than hacking would be a hardware problem.
Start by cleaning your Apple Watch
Then do a forced restart to clear any confused software. Press and hold both the side button and Digital Crown for at least 10 seconds, then release both buttons when the Apple logo appears.
If you still have problems after this the next step would be to unpair and erase, then re- pair to your iPhone. The final last resort is to contact Apple Support and get hands-on assistance at the Apple Store.