My Dog Starts to Shake and Pant

[dhaggerty723]

It just started this past week. She is about 1.5 years old, she's a mix half sheltie and half american eskimo. She weighs about 18 pounds and eats about 2 cups of dry (lamb and rice) food each day and drinks plenty of water.

Just last week, around 10pm we would go to bed, she generally jumps up and hangs with us for about 10 minutes and t hen gets in her dog bed.

Recently (last 5 days) she gets up on the bed, and will start to tremble/shake and pant. This goes on for quite a while, and I'm never sure when it stops, but during the day she's fine. She runs, plays, eats and pees/poops as usual.

Any advice?