Do I need to reset my trends on my fitness?

You could try this, although I am not sure if it actually clears the trends:

• Launch the Watch app on your iPhone.
• Scroll down and tap on Privacy.
• Tap on Reset Fitness Calibration Data

Then follow these steps, and make sure to calibrate your watch too (step 7):

Get the most accurate measurements using your Apple Watch - Apple Support

I do not recommend resetting the fitness calibration data on a regular basis though! Every time you do it, you are essentially taking it back to square one. The more data there is, the better tracking there will be. So unless your Apple Watch is actually acting up and it's visible on a daily basis, only then go ahead with what is written above. If everything seems fine, then just let it be.

If the above does not reset your fitness trends, you could switch to another Apple ID. Or, send a suggestion for such reset feature in here:

Feedback - Apple Watch - Apple