New watch is losing 5 to 15 minutes a day

Try cleaning the battery. The battery is coated when new. I had the same problem loosing 1/2 hr some days then
Ok others

Make sure the voltage on the new battery is correct. Just because a battery is new does not mean it is good. That is likely the problem.

Overhaul is needed for your watch. It has mechanism, and it needs to be serviced every 4-5 years. Just imagine what would your car do without service! So, go and see the watchmaker.

These watches are "automatic" which means that the are self winding.

They will run for 1 -2 days before stopping. Shake the watchgently from side to side for a few minutes and it should start again.

(These watches need to be constantly used to keep them working).

mcdevito75 here, Even a so called new battery could be weak, who knows how long it was in the store before being sold. Try another Battery from another store.

This is usually a indication that the minute hand is slightly loose on its pinion. This requires that the hand be tightened, so that it does not slip. Best left to a watchmaker.

yes it can cause that but it could be otehr things too you have a lifetime warranty send it to skagen they will fix it at very low cost
http://www.skagen.com/service/orderWatchBandParts.fx

The shaking is not the best way to restart the automatic watch as it puts slight strain on watch balance wheel and hairspring (most delicate part in watch).
As watch balance wheel is positioned paralel(leveled) to watch dial, you have to spin your watch back and forth a few times quite quickly.
(Imagine you are turning steering wheel in your car- thats the right motion). Before doing that wind up your watch a few times manually.
Right after doing that observe the seconds hand and if it is ticking just a little bit or ticking back and forth and then stops- your watch has jammed gear train and this is the reason why it stops.
If you don't have seconds hand- after shaking your watch listen for ticking and again- if it stops after short run, the gear train is to blame. In this case you will need watchmakers help as special skills and tools are needed to sort this out.
Do not forget to rate, please.

There is nothing wrong with your watch. Probably it's the one measuring heart rate and pulse (heart beats per second).
Use your users manual to set the watch.
By the way: Timex is one of the worst watch producers.

Because of the way they work, it's quite hard for quartz movements to run consistently slow - so if you find one getting behind, it's usually a sign that it's stopping intermittently. It would do no harm to check that the crown is properly pushed in after you've reset it, but my guess is that the watch will benefit from a new battery. A.