My heart rate suddenly increases

You can check this https://support.garmin.com/en-US/?faq=xQwjQjzUew4BF1GYcusE59

cold weather and lack of a warm up can increase this issue apparently 

Because Garmin did not fix HR algorithm bug that causes the issue, even though it started occuring since 2024 on range of Garmin watches and many people kept reporting it until Varmin said it would fix it. But it never did and ignores the issue.

mine seems opposite, started out way to high then it resets back to normal. all while doing steady state treadmill running. I thought it was better with earlier sw versions. iam on the latest beta

Something similar used to happen to me in the past when I had a heart arrhythmia. Since I didn’t know at the time that I had an arrhythmia, I thought it was a technology issue and I looked for all sorts of solutions. If this starts happening to you almost every day or a few times a week, measure an ECG after your run, since you have it on your watch.

Hellp,

the same appened to me yestarday FW 15.52, never since.

After a Pause it is got crazy, my rhythm was consatnt in that interval

I had this problem 4 minutes into a Strength exercise where I was doing squats and the watch said my HR was 183.   After tightening the strap which wasn't that loose anyway it settled back down so I was wondering whether it was being affected by LED lighting I had on at the time?

I have the same issue with biking. Especially after each active recovery, it takes 30 seconds to raise back.