My 4110 has always done this on occasion, hot or cold. It's definitely not low fluid in my case, and very unlikely it's a restricted filter - mine's been changed at about twice the the recommended intervals and have never had a nasty filter. For the most part it happens when I've got a load of some kind with the loader but it has occurred several times during grass cutting with no load on the front. Doesn't matter if in 2wd or 4wd, happens anytime maybe once or twice in 10-15 hrs. I'd lean towards a sticky valve or spool of some kind in the hydraulics. Don't know if this makes you feel any better but mine has done it for 7 years and 1670 hours but has not gotten any worse or more frequent.