What time is it? Watches and horology

Does anyone elses watch lose time if they wear it when cycling?

I've got one of the cheap Seiko 200m Divers & it's been losing about 3 minutes a week consistently for the last 6 months other than a over the christmas break (when I was wearing a different watch for cycling) & a week when I went on holiday at the start of the month (when I didn't cycle at all).

Would a service sort this or is it just that the watch doesn't like being rattled around at a funny angle?

Stupid question but got to ask - aware of what automatic do?