Hi Lasse,

we hiked in Norway last year and I can highly recommend the Jotunheimer national park. You can go there by bus if you start at Gjendesheim like we did. It not only has the two biggest mountains of Scandinavia around it, but its also perfect if your not sure how many days you want to hike

Simon

I didn't do any winter hiking in Norway, except in the surroundings of Bergen.

Usually it's they don't  recommended to go to more deserted places in winter (oct-April), as it can be very unaccessible sometimes and the weather very unpredictable. Come prepared anyway, with good material and supplies. 

If you pass by Bergen, the Vidden trail (Ulriken-Fløyen) is quite nice and doable in Winter. It probably will fill an entire day in winter. Plenty of accommodation in Bergen. Every starting point is very accessible by public transport. 

Gulfjellet is also nice, weather permitting. Accessible by bus from the city centre of Bergen

The other mountains in and around Bergen are not that much of a challenge, but still quite nice if the weather restricts you from going on the more challenging ones.